In the financial markets here, Treasury Secretary Donald T. Regan is regarded somewhat quizzically. Although Regan made his reputation (and a considerable fortune) on Wall Street running Merrill Lynch, the typical money manager here (Republican or Democrat) shrugs Regan off as "just a salesman," and is skeptical of his innate financial wizardry.

This is somewhat unfair, because Regan was an innovator who shook up the Wall Street establishment, forcing lower commissions. "I have never believed in not rocking the boat," Regan proudly told a group of reporters a few weeks ago in discussing Wall Street.

What riles the financial men at the moment is a speech Regan made Sept. 8 to the Chemical Manufacturers Association in Washington. He not only jawboned bankers to lower their interest rate charges but, more important, denied that the huge budget deficits facing the nation over the next several years are a major cause of high interest rates.

In brief, Regan says that the Treasury has made an "exhaustive study of the subject, and there is simply no empirical evidence that correlates deficits and interest rates. . . . I am not saying deficits are not a serious matter. They cause a lot of problems. It just happens that high interest rates are not one of them."

This view separates Regan not only from most economists, in and out of Wall Street, but from economic council chairman Martin S. Feldstein, who has made at least a dozen speeches in the past few months blaming high interest rates on budget deficits.

In a telephone interview following Regan's speech, Feldstein said he would not comment directly on the secretary's position. But speaking as an economist on the theory Regan outlined, Feldstein put on the record exactly how he feels:

"I can understand why some people say there is no correlation between deficits and interest rates: They are focusing on nominal (market) interest rates, which have come down.

"It's nevertheless true that the interest rates that matter are real interest rates (subtracting inflation from market rates). Real interest rates are the ones that cause the 'crowding out' of investment. So this discussion about correlations (between interest rates and deficits) is really beside the point."

But the most important thing, Feldstein said, is that the "correlation" theory doesn't take into account the huge anticipated "structural" deficits in the next several years--the kind that won't be reduced by economic recovery.

"Unfortunately," Feldstein said, "the deficits we see for the next half- dozen years are unprecedented. We're looking at numbers on the order of 5 percent to 6 percent of gross national product. There is no empirical evidence of how these huge deficits will affect real interest rates."

Henry Kaufman, interest-rate seer for Salomon Bros., also pooh-poohed Regan's theory. He told me: "There is just no doubt that if the deficits had been lower in the last year of recession, interest rates would have been substantially lower." Like Feldstein, Kaufman stressed that what worries econmists and financial men is the pileup of deficits in the future, as far as the eye can see.

"The correlations that Regan talks about are spurious," was the blunt comment of analyst Sam Nakagama of Nakagama and Wallace.

The business-financial community takes Regan's blast as one more piece of worrisome evidence that the Reagan administration is unwilling to face reality: that some combination of tax increase and spending reductions will be necessary to bring down the deficit.

Regan first trotted out his benign theory at the Williamsburg economic summit. He was hooted down by German Economics Minister Otto Lambsdorff and others in one of their private meetings.

In partial proof, Regan cites the fact that Japan and West Germany typically have larger budget deficits than the United States, as a percentage of GNP, and yet have much lower interest rates. What Regan failed to say is that the level of private savings is much higher in Germany and Japan than in the United States. That means those governments can finance deficits without the fierce competition for funds that drives real interest rates higher here.

The common view in New York is that so long as the president and Congress demonstrate no interest in cutting back the deficit, long-term interest rates will remain high, regardless of Regan's Treasury study. They are quite sure that Ronald Reagan and the "pols" in the White House would rather believe Regan on this point than Feldstein.

Regan isn't troubled by his low marks in Wall Street. "(They) like stability and caution," the secretary said on another occasion, "and I have never been stable or cautious, in Wall Street's opinion." But the obvious split with Feldstein on this issue is more significant, and remains to be resolved.