The FBI, suspecting 2 1/2 years ago that retired CIA analyst Larry Wu-Tai Chin was spying for China, intercepted his mail, tapped his home telephone phone and searched his luggage at Dulles International Airport as he left for a trip to Hong Kong, according to papers filed yesterday in federal court in Alexandria.

During this period of intense surveillance, Chin continued to work as a consultant for the CIA, from which he retired in l981, and at one point was asked to return to the agency full time, according to his lawyer.

Sources familiar with the case said the CIA cooperated with the FBI investigation from its inception.

Prosecutors have notified Chin's lawyers that they plan to use the electronically gathered evidence at his Feb. 4 trial on charges of espionage. Until now, much of the prosecution evidence made public has rested on statements Chin made during a six-hour interview with FBI agents on Nov. 22, the night he was arrested.

Chin, 63, who also is charged with conspiracy and income tax and financial reporting violations, appeared yesterday in U.S. District Court for a hearing that was closed under the Classified Information Procedures Act, according to Assistant U.S. Attorney Joseph J. Aronica.

Chin's attorney, Jacob A. Stein, declined to say what happened during the hearing and Aronica would say only that "informal agreements on how we will proceed" were discussed.

Papers filed Thursday in preparation for yesterday's hearing said the session was to hear arguments from Chin's attorneys that evidence from the luggage search should be suppressed on grounds that it violated Chin's constitutional rights. They had also asked U.S. District Judge Albert V. Bryan Jr. to facilitate their review of classified summaries of "tens of thousands of monitored conversations" in time for the trial.

The defense team received the summaries and 400 pages of classified documents on Thursday.

Prosecutors demanded this week that Chin, who translated classified documents for the CIA, provide more details about classified information he intends to introduce in his defense at trial, according to court papers.

Chin is accused of spying for China since 1952 and allegedly met with Chinese intelligence officials as late as March.

Authorization to place Chin under surveillance was first given April 14, 1983, by the U.S. Foreign Intelligence Surveillance Court as part "of an ongoing foreign counterintelligence investigation," according to papers filed by the government.

The court, a special federal panel to approve surveillance in foreign spy cases, approved both telephone and microphone surveillance. But FBI agents "never made entry into Chin's premises to install the microphone devices," the documents say.

On May 27, 1983, after the court "had found Chin to be a foreign agent," the attorney general authorized the search of Chin's luggage. This took place three days later when Chin checked his suitcase for a flight to Hong Kong, the papers said.