The Justice Department yesterday dropped its bribery and conspiracy indictment against South Korean businessman Tongsun Park, the key witness in the long-running investigation of Korean government influence buying in Congress.

Government prosecutor John Kotelly moved to dismiss the charges in a brief appearance before U.S. District Court Judge June Green. The action was the final note in the trouble-plagued investigation of allegations that Park, a flamboyant Washington party-giver, and Korean diplomats made large cash gifts to members of Congress in the early 1970s in a lobbying campaign to assure continued U.S. foreign aid.

Only a handful of prosecutions were brought and only one member of Congress, former representative Richard T. Hanna (D-Calif.) went to prison.

Kotelly told Green that Park had "substantially complied" with the agreement he made with then Assistant Attorney General Benjamin R. Civiletti in December, 1977 in Seoul. Park agreed then to return to the United States and testify truthfully in exchange for eventual dismissal of the charges against him.

Civiletti was sworn in yesterday to succeed Griffin B. Bell as attorney general. Park's attorney, William G. Hundley, said that Park was planning to send a congratulatory telegram to Civiletti, his old Adversary.

Dismissal of the charges was expected because the perjury charge against former representative Nick Galifianakis (D-N.C.) -- the only remaining Korean investigation case -- was dismissed last week on technical grounds by another judge.

Kotelly said he had reviewed Park's change of testimony in a case that forced the government to drop perjury charges against New Jersey rice dealer Grover Connell. But he decided that he discrepancy did not warrant a perjury charge against Park, he said.

Yesterday's action frees Park to re- turn to Washington, where he gained attention in the early 1970s as an entertainer of congressional dignitaries. But there is some question whether the Korean government would issue an unrestricted passport to the man who focused such adverse public attention on his country.

Hundley said Park told him in a recent phone call from Seoul that he has no intention of moving back to the United States permanently. But Hundley noted that Park still faces a Tax Court trial over some $4.5 million in taxes the Internal Revenue Service claims he ownes.

Hundley said that Park has sold two homes in Washington for more than $1.1 million, but that the government is holding the money until the tax case is settled. The government also holds furnishings and personal property totaling more than $200,000 and has filed a lien against the Park corporation that owns the George Town Club in Washington.

"They've got plenty tied up to cover the ($4.5 million) liens," Hundley said.

Park left Washington in the fall of 1976 after he was questioned by Justice attorney Paul R. Michel about payments to members of Congress. Park stayed in London after The Washington Post began publishing a series of stories saying he was the key figure in a vast Korean-government-sponsored lobbying campaign.

Park was indicted secretly by a federal grand jury in Washington in late August 1977, on charges he conspired to bribe Hanna and others.

Prosecutors hoped to used the sealed indictment to nab and extradite Park from a neutral country. But The Washington Post reported that Park had been indicted and it took four months of negotiations before he agreed to return and testify.

During questioning in Seoul, Park spelled out details of cash payments to dozens of congressional friends. Later in televised appearances before the House committee conducting a parallel investigation of colleagues' ethics, Park gave colorful and stunning testimony about passing envelopes filled with $100 bills to members of Congress.

His recollections, backed by personal ledger books and diaries, led to House disciplinary proceedings against four current members. Three -- Reps. Charles Wilson, Edward Roybal, and John J. McFall all California Democrats -- were reprimanded. The House committee investigating the charges recommended no action against Edward J. Patten (D-N.J.).

Park's testimony also led to the perjury charges against Connell and Galifianakis and bribery charges against former representative Otto E. Passman (D-La.), who was acquitted.