Prosecutors introduced evidence yesterday undercutting testimony by former White House deputy chief of staff Michael K. Deaver about his work as a lobbyist for the South Korean government and his support for appointment of a special presidential envoy to Canada.

In both instances, prosecutors produced documents and witnesses tending to reinforce charges that Deaver lied to a congressional subcommittee and a federal grand jury.

The former White House aide is accused of attempting to cover up his actions in an effort to save the flourishing lobbying business that he established within months of leaving the White House in May 1985.

Yesterday, the eighth day of testimony in the U.S. District Court trial, saw the first testimony about Deaver's actions in the Reagan administration.

Robert Kimmitt, a former National Security Council official, said Deaver voiced support for appointment of a special envoy to Canada to work on acid-rain pollution several weeks earlier than he had disclosed to a grand jury.

Kimmitt, a Washington lawyer, said he wrote on a White House routing slip after a mid-February planning meeting for a 1985 meeting between President Reagan and Canadian Prime Minister Brian Mulroney that "Deaver is still keen on the special representative."

That was a reference to a proposal for appointment of special envoys from both governments to seek a solution to Canadian demands that the United States curb pollution from plants near the border, he said.

Documents attached to the slip disclosed that Edwin Meese III, then White House counselor, and members of the domestic policy staff expressed opposition to appointment of special envoys, fearing that they would "serve only to magnify" U.S.-Canadian differences on the issue.

Kimmitt's statement was one of the strongest that prosecutors have produced in their case against Deaver, the first person indicted as a result of an investigation by an independent counsel named under the 1978 Ethics in Government Act.

In testimony to the grand jury investigating him on ethics issues, Deaver, whose lobbying firm represented Canada, said he did not recall the idea of a special acid-rain envoy coming up until a March 1985 summit planning meeting.

But Kimmitt said his memo about the envoy was apparently written Feb. 15, 1985. "I don't have any specific recollection of it or why I wrote it," he said.

Nonetheless, Kimmitt said he recalled saying at the planning meeting that summit "preparations are going well except that the acid-rain issue is a sticking point."

At that point, he said, Deaver interjected, asking, "Doesn't the special representative idea take care of that?"

Doral S. Cooper, a former associate in the lobbying firm, told how she and Deaver went to South Korea to work on the firm's $475,000 account with the government and helped lay groundwork for a letter from President Chun Doo Hwan to Reagan on trade issues.

Prosecutors have accused Deaver of attempting to conceal his work on that issue from a House subcommittee, while Deaver has said he had done nothing to help Kim Kihwan, a Korean trade emissary gain entry to the Oval Office.

Prosecutors displayed a color photograph of that meeting yesterday, showing Kihwan handing Reagan the letter that Cooper said Deaver and the firm had helped draft.

Rear Adm. John M. Poindexter, former national security adviser, has testified at the trial that Deaver called him asking whether the meeting had been placed on the president's calendar.

A White House photographer testified yesterday that the session lasted from 11 a.m. to 11:02 a.m., and he produced a presidential schedule that showed the appointment written in script.

Cooper verified documents that Deaver's firm filed with the Justice Department under the Foreign Agents Registration Act that showed the company reported a meeting with Gaston J. Sigur Jr., a National Security Council staff aide, on trade issues.

The initial report, dated April 18, failed to mention that Cooper and Deaver were the individuals who met with Sigur at his office.

That fact was added on a supplemental filing dated June 27, weeks after Deaver told the congressional panel May 16 that he could not recall other contacts with NSC staff aides. Prosecutors say Deaver attempted to conceal the Sigur meeting.

Prosecutor Whitney North Seymour Jr. stated in his opening argument that then-White House chief of staff Donald T. Regan discovered the Kihwan meeting on the president's schedule and ordered it removed. Seymour said Deaver had to scramble to have it restored.