Former President Nixon has agreed to allow public access to the bulk of 600,000 documents he donated to the U.S. government concerning his years of government service before became president, according to documents filed in federal court here yesterday.

The agreement by Nixon, which represents a major reversal of his position concerning access to such materials, ends a lawsuit that has been pending for more than four years seeking release of what have come to be known as his "vice presidential papers."

In the correspondence filed here, yesterday U.S. Archivist James B. Rhoads said it was the first time Nixon had allowed public access to materials he donated to the government and described it as a "welcome development."

The agreement still blocks access to materials clearly concerning national security or possible invasions of personal privacy, but persons familiar with the documents say few of them should fall into those categories since they were initially screened by Nixon's own staff before he donated them to the government in 1968 and 1969.

Nixon's letter to General Services Administrator Jay Solomon proposed the change in the rules of access set forth in the deeds giving possession of the documents to the government.

"I now find that due to the time elapsed since the date of the conveyances (of the materials), the necessity for total closure of the materials no longer exists, and it is now possible to open the materials in certain respects for research and historical use," Nixon said in the letter, which was dated March 22.

The amendment to the deeds came three months after the U.S. Court of Appeals ordered U.S. District Court Judge Joseph C. Waddy to reinstate the suit brought by Robert M. Brandon, head of the Tax Reform Research Group, a Ralph Nader-connected group. Waddy had dismissed the case, saying the documents were exempt from the Freedom of Information Act, which could have required disclosure.

"Basically, we wanted to free the documents up for scholars," said Brandon's attorney, Alan B. Morrison, yesterday. He also said the suit was filed at a time that controversy surrounded Nixon's claim that the donation of the materials was tax-deductible, so the Nader-connected tax group was interested in that aspect.

Nixon's attorney, R. Stan Mortenson, said yesterday the time "seemed to be right" for allowing public access to the documents and end the litigation over the material.

Mortenson denied speculation that the decision to allow access to the documents was made so Nixon would not have to undergo questioning in civil depositions about the controversial donation of the papers to the government.

An investigation by the Watergate Special Prosecution Force and other investigative bodies showed that a deed used in connection with the donation was backdated so Nixon could receive tax benefits in connection with the gift. Nixon lawyer Edward Morgan was convicted of defrauding the government for his role in backdating the deed.

At the time of the original donations in 1968 and 1969, Nixon placed detailed restrictions on access to the papers until his terms as president ended. When he resigned from the presidency in August 1974, he signed new deeds extending the restrictions on access to 1985.

The materials are stored in 1,176 boxes under the following five general categories, according to the most recent accounting of them: General Correspondence as Vice President, Appearance File 1948-1962, Correspondence re Invitations 1964-1961 Foreign Trip Files as Vice President and Visit of Khrushchev to the United States.

Rhoads said in court papers filed yesterday that his office "will promptly review the subject materials to identify and segregate materials that fall under the two restriction clauses and open the remainder for public use."

Rhoads said the material should be available to the public within 120 days.