Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) said yesterday that President Reagan should reappoint Paul A. Volcker as chairman of the Federal Reserve Board when his term expires in August.

Baker said that he has urged the president several times to reappoint Volcker as chief of the Federal Reserve, which sets the nation's monetary policy. Baker said that the reappointment would help the nation's economy.

Baker, who was interviewed on "Face the Nation" (CBS, WDVM), also said that because Volcker is a "known quantity," his reappointment "would have a calming and tranquilizing effect on the world economy."

Volcker was named chairman of the seven-member Federal Reserve Board in 1979 by President Carter. Although Reagan has said that he has not yet decided whether to reappoint Volcker, several top White House officials have said privately that they think Volcker should be replaced.

The Reagan aides say that they think the public holds the Federal Reserve responsible for high interest rates and the severe recession. They also apparently worry that a Volcker-led Federal Reserve will be so sensitive to price stability that if it detected a possible resurgence of inflation, it might tighten monetary policy immediately and potentially choke off the economic recovery.

The two leading candidates mentioned as possible successors to Volcker are former Council of Economic Advisers chairman Alan Greenspan and current Federal Reserve vice chairman Preston Martin, a Californian appointed to the board by Reagan 18 months ago.

Most executives on Wall Street seem to favor Volcker's reappointment, although most also are said to believe that Reagan has already decided to replace Volcker.

Baker said that he thinks that if the president decides against reappointing Volcker he would favor Greenspan. Greenspan, who heads a New York economic consulting firm, has said that he supports Volcker's reappointment.

In a wide-ranging interview, Baker also said:

* He would support sending a small number of additional military advisers to El Salvador but would not favor sending troops. He said that the civil war in El Salvador will be "decided in Moscow and Washington," and that he hopes Reagan and Soviet leader Yuri V. Andropov will begin discussing the situation in Central America. Baker said that the United States cannot do any less than it is doing in El Salvador and other Central American nations. "We cannot stand by and see the Soviets export mischief to Central America while we stand idly by."

* There will be no major changes in tax law this year.