Romuald Spasowski is an old-school diplomat, a strikingly handsome intellectual who had become openly sympathetic with Poland's Solidarity movement.

He joined the communist party while a member of the Polish underground in World War II, and was his nation's senior diplomat when he accepted political asylum in the United States yesterday.

Spasowski, 61, began his second tour as Polish ambassador to this country in 1978. He talked about heading "an open embassy" and building bridges to western businessmen and intellectuals. When John Paul II, a fellow Pole, was named pope in 1978, Spasowki threw a party at the Polish embassy on 16th Street. His wife, a devout Catholic, attended Mass regularly.

"He's more a Catholic than a communist," one Polish diplomat complained.

A scholarly, urbane man more comfortable with western intellectuals than hard-line communists, Spasowski has a long aristocratic face with a small white goatee. He looks like the subject of one of the fine 19th Century oil paintings that decorate the Polish embassy.

He appeared sympathetic with the Solidarity movement from the time it was launched in 1980.

With his country suffering massive financial problems and the embassy hard pressed for money, he all but gave up entertaining in the months that followed. His wife, Wanda, served as her own housekeeper at their official residence in the Forest Hills section of Northwest Washington. The few official functions they hosted were spartan affairs, often with crackers and cheese as the only fare.

In recent months, both became increasingly open about their support for reforms, and their optimism for a new free Polish society.

Word of this apparently reached superiors in Warsaw. A month ago ago, Spasowski was told he would be relieved of his ambassadorship six months before his tour would normally end, and be forced into retirement.

But Spasowski continued to serve as ambassador. He was at the State Department every day last week. And he was the official that Secretary of State Alexander M. Haig Jr. summoned to protest the martial law declaration last weekend, and the mass arrests that followed.

Tensions, meanwhile, ran high in the Polish embassy in Washington. According to one Polish diplomat, the ambassador refused to share with subordinates the last message from Warsaw outlining the reasons for the martial law declaration.

Spasowski is well known in diplomatic circles. This is his fifth ambassadorial post, and before coming to Washington on his current tour he was the No. 2 man in the Polish foreign ministry. He also coordinated the visits of three American presidents--Nixon, Ford and Carter--to Poland.

Those who know him were not overly surprised by his request for political asylum, or with the powerful language and dignity with which he announced his intentions.

"He is like so many high officials in the government," said Richard Davies, a former U.S. ambassador to Poland. "He is a patriotic Pole first, and a communist second. He has strived throughout his career to establish good relations with the U.S., and other western countries."

White House counselor Edwin Meese III, questioned on "Meet the Press" (NBC, WRC) said the defection indicated "the seriousness of the internal problems within Poland."

In many ways, Spasowski is symbolic of the best of a diplomatic breed. The son of a university professor, he joined the underground when the Nazis took over Poland during World War II.

"All of us worked for the underground," his wife told The Washington Post last summer. "I used to carry anti-Nazi pamphlets from the printing presses to the distribution points. Once I was stopped and the Nazi officer examined my shopping bag and my pockets, but I had the pamphlets in my muff, and he didn't think to look there."

Spasowski fled to the Soviet Union in the early 1940s, and became an officer in an ex-patriot brigade called the "Berling Army." The army fought its way back into Poland beside the Russians, and when the war ended, Spasowski joined the Polish foreign service.

His first assignment was as a military liaison in West Germany; later he was named consul in Dusseldorf. He rose rapidly, serving first as ambassador to Argentina, and from 1955 to 1961 as ambassador to the United States. He later headed the Polish mission in Saigon.

But his most impressive act as ambassador was his last. Standing before cameras at the State Department, he spoke not of himself or his family, but of his homeland.

"I turn to you Americans who are listening to me and watching me now," he said in emotional tones. "At this very moment, when you sit in front of your TV sets, evil forces crash on Poland and its deeply patriot and religious people. Think about those Poles, try to imagine their lot . . . . Remember they are the best sons and daughters of my country, those workers, those students, those intellectuals.

"Whatever the future will be, don't be silent Americans."