Martin Feldstein, President Reagan's new chairman of the Council of Economic Advisers, has "come as close to putting together a Walter Heller council" in terms of brains as anyone since, economist Otto Eckstein commented last week.

The comparison may seem odd to Democrats who remember Heller's time at the CEA under presidents Kennedy and Johnson as the heyday of liberal economics. Feldstein and his staff are conservative and free market-oriented. They work for the most conservative president since World War II.

But the batch of young economists that has joined the Council of Economic Advisers in the last month, several of them brought here by Feldstein, is "certainly the most capable collection of young economists in Washington," Eckstein said.

Others agree that Feldstein, himself a noted academic economist who is widely expected to raise the quality of economic advice available to the president, has a group of very bright people. Many of them are new to Washington and enthusiastic about what they can do and learn here.

Heller had noted economists such as Robert Solow, Kenneth Arrow, and the late Arthur Okun on his staff, while last year's winner of the Nobel Prize for economics, James Tobin, was one of the other two council members. The CEA also had "quite a coterie of consultants," Heller recalled last week, including Paul Samuelson of MIT, Joseph Pechman, now outgoing director of Economic Studies at Brookings Institution, and Charles Schultze, CEA chairman under President Carter.

Among those brought here last month by Feldstein are:

* Lawrence Summers, 27, PhD Harvard. Perhaps the best known of the new recruits, Summers is described by colleagues as a "brilliant economist" who is "unusually talented." He was fought over by Harvard and MIT for a full professorship, Eckstein said, adding, "you can't knock that." Summers is a former graduate student of Feldstein's and has worked closely with him for several years. He has studied several of the issues that Feldstein has worked on, doing research on taxation and its effects on investment, on unemployment and unemployment insurance. He is not an economic forecaster but is thought likely to work on aspects of domestic economic policy and the budget.

* Paul Krugman, 29, PhD MIT. Another academic superstar, Krugman has been an associate professor with tenure at MIT and "one of the two best international economists to come along" recently, according to one older economist. Feldstein describes him as a particular specialist in international finance.

Daniel Frisch, 29, PhD Harvard. Frisch, also a student of Feldstein's, has worked as his research assistant for about eight years. Frisch started in his sophomore year as a "number cruncher" for Feldstein, who then got him interested in economics. A tax specialist, Frisch is on leave from the University of Washington in Seattle, where he is an assistant professor.

* Stephen McNees, 40, PhD MIT. McNees, a macroeconomist and forecasting expert now on leave from the Federal Reserve Bank of Boston, was encouraged to come to Washington by William Poole, who this summer was chosen by Feldstein's predecessor, Murray Weidenbaum, to fill a vacant spot as one of the council's three members. Poole, on leave of absence from Brown University, where he is the head of the Economics Department, has been working as a consultant for the CEA for the last few weeks, his formal nomination to the council delayed by Feldstein's nomination and confirmation. McNees is described as a good technician and forecaster.

In addition to Poole, McNees likely will work on forecasting with senior staff members Lincoln Anderson, Adrian Throop and Robert Villanueva, one CEA staffer said.

Feldstein also persuaded Lawrence Lindsey, a graduate student of his who had just returned to Harvard this summer after a year at the CEA, to return to Washington with him. Lindsey falls somewhere in between the otherwise separate categories of junior and senior staff, one official said.

The CEA does not work like other government agencies. Its small professional staff consists largely of academic economists, on leave of absence for a year or two, rather than of civil servants. The junior staff is generally made up of graduate students, while the senior staff is composed of PhDs with "three to 20" years of experience, a staff member said. It's the "dream of a lot of academic economists to work on the council," one of Feldstein's new recruits said, adding he believes that "Marty will be most energetic and effective."

Feldstein has bumped the staff up to 25 professionals, excluding the council members. It fell to below 20 last year, having shrunk considerably over the past decade, a spokesman said.

Feldstein also has recruited as junior staff members David Reitman, a graduate student at Stanford; Robert Myer, who joins the CEA ranks Monday from the Urban Institute; and Gregory Mankiw, graduate student at MIT.

"The thing that most clearly unites" the staff is "our market orientation," Poole said last week. "All of us feel government should have a less pervasive economic role in our society," he said. There is a natural division of labor between Feldstein, "an acknowledged and distinguished expert" on fiscal policy, and Poole, a monetarist who has worked primarily on monetary policy issues and been an active consultant to the Boston Fed, Poole said.

Feldstein remarked last week that he could think of no "grand way to say what I want to do, other than good economics." The staff members between them cover more or less every area of importance, he said, and can deal with the broad range of issues which comes to the CEA.

Apart from the usual tasks of monitoring and forecasting the progress of the economy, and being involved in budget discussion, the CEA recently has been involved in work on issues from private pension policy to agriculture to international currency problems, Feldstein said.

Its influence obviously depends critically on how the president treats its advice. From the outset of the Reagan administration, the CEA's role was downplayed. Weidenbaum, who resigned as chairman this summer, was not chosen for some weeks after Reagan's other key economic players.

Office of Management and Budget Director David Stockman already was hard at work on the blueprint for Reagan's economic program before Weidenbaum was installed. Treasury Secretary Donald T. Regan was designated by the president as the chief economic spokesman for the administration.

Weidenbaum managed to restrain the wilder optimists in the administration's earliest forecasting round, sources say. But in general he was not very influential within the administration, and did not have a strong reputation, administration officials say.

Feldstein has started out by briefing the president and others on the outlook for the economy, and clearly is hoping to have an impact on policy. "I am the economist in the White House," he asserted last week. In his confirmation hearings he criticized overly optimistic forecasts of a painless end to inflation and has cautioned that growth should be, and probably will be, only very moderate next year.

As part of his role as resident economist, for example, Feldstein called Regan and Federal Reserve Chairman Paul Volcker before the release of the government index of leading indicators last week to give them the number and discuss it, and wrote a memo on the news to the president.

"That doesn't stop everyone and his brother" from having an interpretation of their own circulated, he said. But he hopes over time to build the council's reputation for accurate, and useful, analysis.

"I have very broad interests," Feldstein said. These include taxation -- in particular its effects on incentives to save and invest -- unemployment and inflation. Although a conservative and a believer in shrinking government, Feldstein said last week he thought part of the long-term structural unemployment -- which the CEA is thought likely to start working on soon--could be dealt with only through on-the-job subsidies for some less employable people.

One Republican economist thinks that the new council's influence inevitably will be restricted by the president's own unwillingness to back off his economic program any more than he has. "Marty is very wise" to bring his own people down here, he said. But without a president willing to listen, the CEA's impact will be limited, he said.

Heller said the White House obviously has to be persuaded that relying on the CEA will not only improve economic policy but also make the president more effective and serve him well politically. Despite his doctrinaire differences with the conservative Feldstein, he said, "it's delightful to see the council being beefed up with really first-rate economists."

President Nixon's CEA Chairman Herbert Stein remarked, "The council staff has always included a lot of brilliant people . . . it's always been one of the strengths of the council to have people fresh from the academic world." Now that many of the original supply-siders have left the administration, there is plenty of good advice available to Reagan, Stein said. The main problem is the need for new thinking in the economics profession itself, he said, "but that won't come out of the council," nor can it be made to order.