Secretary S. Dillion Ripley of the Smithsonian Institution agreed yesterday to change some of its budgetary practices that were criticized by investigators for the House Appropriations Committee, but argued that many of the findings of the sharply worded report were "incorrect and unwarranted."

Ripley denied the major finding of the nine-month study, which said the Smithsonian was "exercising a deliberate policy . . . to avoid accountability" for the more than $100 million in public funds it receives annually.

In a separate written response to the charges, the Smithsonian said "we admit the justice" of some criticisms, and promised "to correct them." In other instances, however, the Smithsonian said "we accept the investigators' finding but disagree with their interpretations."

House investigators accused the Smithsonian of juggling employes between public and trust and fund payrolls, spending public money for private purposes launching massive projects without approval of its board of regents and becoming profit-oriented.

Ripley said the 17-member board of regents, in an emergency session last Saturday, agreed to consider meeting four times a year, instead of three, in an effort to become better informed about Smithsonian activities. The blue-ribbon board includes Chief Justice Warren Burger, Vice President Walter Mandale, members of Congress and representative of the public.

The investigative report, revealed by The Washington Post on Feb. 4, was made public yesterday at the start of two days of hearings before the House Interior Subcommittee on the Smithsonian's 1979 budget request.

The day-long hearing chaired by Rep. Sidney R. Yates (D-Ill.), produced no bombshells, but rather dramatized the difficulty of requiring the world-famous complex of museums and research laboratories to comply with rules established for less exotic federal agencies.

Ripley and his high-ranking associates repeatedly stressed the unique character of the Smithsonian, which has for more than a century received money from a variety or sources, with a variety of strings attached. In recent years, however, it has become more and more dependent upon public money.

David Challinor, assistant secretary for science, gave one example of why the Smithsonian occasionally switches some of its 4,500 employees between public and trust fund payrolls.

When the Smithsonian built a multi-said, expert technicians were transferred there from the Smithsonian Astrophysical Labortory in Cambridge, Mass.

In Cambridge, the technicians were employed as trust fund employes, paid for the proceeds of a Smithsonian contract with NASA. In Arizona, they were paid with funds appropriated directly from the federal treasury. After six months, they returned to Cambridge, and switched back to the trust fund payroll.

Rep. Jamie Whitten (D-Miss) told Ripley that with $109 million requested in 1979 federal funds, "we have a right to know how it's being used, if there is a whole lot of play-around money."

Ripley agreed, and said later in the hearing "it is not our intention to go on the dole. To become totally dependent upon public appropriations would be an absolute betrayal" of the institutions' charter from Congress, and its acceptance of trust money, Ripley said.

"It's easy to get the impression [from the investigation] that we are playing some kind of a shell game," Ripley said. "But nothing would be more distasteful."

When Yates asked about staffing of "the Fort Pierce bureau," which was criticized by the investigators, he got a lecture from the scholarly Challinor on the glories of studying sipunculids, which he explained is "a soft-bodied worm the size of your finger that is able to penertate rocks.