ALEXANDRIA, Va. (AP) _ Convicted spy Larry Wu-tai Chin, who realized $180,000 in espionage earnings over a 30-year period, gambled with a passion that contrasts with his courtroom demeanor as a scholarly CIA translator.

Chin's diaries, entered as evidence in his trial, show he paid at least $96,700 to Las Vegas casinos and visited gambling clubs while on trips to meet Chinese intelligence contacts in London and Macao, the Portugese colony on the Chinese coast.

Chin's love for blackjack was made clear in a Feb. 2, 1980, letter to the Sands in Las Vegas in which he complained that the casino had allowed him to exceed his credit by 75 percent, or $6,000, a month earlier.

''When I was suffering from a hopeless losing streak and insanely throwing good money after bad, instead of stopping me at the limit of my credit line, as all pit bosses would have done as a matter of course, a pit boss granted me thousands after thousands of dollars to bet,'' Chin said in the letter.

It went on to say he was back the next day for more.

''Under such mental strain, the $7,000 I brought in was soon drawn into the whirlpool the next day,'' he said in the letter, part of the evidence entered against him at U.S. District Court in Alexandria.

Chin did not allow gambling to devour all of his illegal fortune, however. With advice from a real estate specialist, he bought properties in Virginia, Maryland, Nevada and California.

At the time of his arrest last Nov. 22, he owned 29 rental units valued at more than $700,000, according to the evidence.

The papers show that Chin, convicted last Friday of spying for China over a 30-year span, paid Las Vegas casinos $96,700, transferring $25,000 in installments from Hong Kong banks where he collected his spy fees.

Testifying in his own defense, Chin acknowledged that he did not report the income or the transfers for fear of disclosing his spying activity. The transactions apparently were not detected by federal authorities, despite seven audits of Chin by the Internal Revenue Service.

Chin's taste for gambling conflicted with the image the lean 6-footer presented in court of a calm, bespectacled Oriental scholar who favors gray suits, quiet ties, black shoes, and was described by his CIA boss as ''one of the best Chinese language monitors we ever had.''

Chin told friends he had a mathematical system for winning at blackjack, and that he used his winnings to buy property.

Assistant U.S. Attorney Kent S. Robinson, a prosecutor in the case, declined to speculate whether Chin lost more than he won gambling, although the evidence showed that his credit had been cut off by two Las Vegas casinos, the Sands and Caesar's Palace.

Robinson and other federal officials interviewed this week said there is no system for monitoring overseas bank transfers of less than $10,000.

Chin's diaries show he transferred $5,000 to the Sands on Aug. 2, 1979, and $8,000 there on Feb. 18, 1980. They show he moved $6,000 from Hong Kong to an unspecified Las Vegas casino on April 6, 1982, and another $6,000 on July 7 the same year. He paid the balance of his debts to the casinos in cash or through U.S. banks.

The evidence also shows he transferred an additional $35,679.73 from the Hua Chiao Commericial Bank and $48,304.80 from the Hong Kong Shanghai Bank to U.S. accounts in his name.

Prosecutors said the money was deposited in Hong Kong by Chinese intelligence officials to compensate Chin for his 30-year espionage career.

He collected at least $180,000 for his spying, but testified at his trial that he was motivated by dual patriotism - a desire to bridge the political gap between his native China and his adopted land, the United States.

The jury took three hours and 24 minutes to convict him on a 17-count indictment: six of espionage; five of falsifying his income tax returns; and six of concealing foreign bank accounts.

He faces two possible life sentences, 83 additional years in prison and fines of up to $3.3 million. Sentencing is scheduled for March 17.