Poland's ambassador to Japan, Zdzislaw Rurarz, requested and was granted political asylum in the United States, saying he could not tolerate the upheaval caused by the military crackdown in his country, Japanese Foreign Ministry officials disclosed today.

Rurarz, a 51-year-old diplomat and foreign trade expert, boarded a plane for the United States this evening about 30 hours after he appeared unannounced at the American Embassy in Tokyo to seek asylum. He was accompanied by his wife, Janina, 49, and 25-year-old daughter, Ewa.

Rurarz arrived in Washington late Thursday, news services reported.

American officials in Tokyo confirmed the Foreign Ministry's account but declined to provide further details.

Rurarz's action followed a similar move earlier in the week by Poland's ambassador to Washington, Romuald Spasowski. Rurarz was hustled out of Japan under heavy police security without making a public statement, however, in contrast to Spasowski's dramatic defection announced before the American media.

Senior Foreign Ministry official Yoshiya Kato said that during a one-hour meeting with Rurarz last night the Polish diplomat expressed a firm conviction to defect, citing his "deep disappointment" with Poland's military rule. Kato said Rurarz told him he had decided to go to the United States "because it's a free country, friendly to Poland," where he hoped to "continue his fight against the present Polish regime."

According to a Kyodo News Service report quoting Tokyo police officials, Rurarz told them that he could no longer represent a Polish government that denies fundamental human rights to the Polish people.

Rurarz was quoted as telling the police that Poland's martial-law government had imposed a "state of war" on the country that "runs counter to the interests of the Polish people and serves the interests of Soviet imperialism."

Foreign Ministry officials said that after Rurarz appeared with his family yesterday, the U.S. Embassy quickly obtained State Department approval and granted asylum.

An American Embassy official said Rurarz, who has been ambassador here since February, "requested asylum and it was granted through the proper channels." Reliable sources said that U.S. Ambassador Mike Mansfield telephoned State Department officials to convey the request while Rurarz waited in his office and that approval was immediately given.

Rurarz had openly supported Poland's Solidarity labor movement during his tenure as ambassador and warmly greeted Solidarity leader Lech Walesa when he visited Japan in May as the head of a nine-member Solidarity delegation, Japanese press reports said.

Rurarz, a former economic adviser to former Communist Party leader Edward Gierek, served from 1962 to 1968 as economic attache in the Polish Embassy in Washington, Reuter reported.

Japanese Foreign Minister Yoshio Sakurauchi called Rurarz's defection "a severe indictment of the future of his country."

The Polish Embassy, in a statement confirming Rurarz's departure for the United States, said that the attitude of the Polish government "will be expressed in proper time."

Echoing Tokyo's cautious stand on recent events in Poland, Prime Minister Zenko Suzuki said earlier today that Japan would continue to consult closely with the United States before deciding whether to join Washington in imposing economic reprisals against Warsaw such as those announced by President Reagan Wednesday night. Suzuki said, however, that Japan would carry out commitments on bank loans and food supplies.