Nationalist Chinese Ambassador James C. Shen left Washington last night, escorted to his departure by a crowd of flag-waving, sometimes weeping friends and supporters making their farewell not only to a friend, but in some ways to a country.

Shen left Washington after seven years here not like most ambassadors, because his tour of duty is up, but because on Jan. 1, the Communist regime in Peking will be the official Chinese government recognized by the United States, not the government in Taipei that Shen represented. As some people wiped tears from their eyes and others shouted "Ching hwa ming kwo wan shui" (long live the Republic Shen was engulfed in a mass of about 200 well-wishers, trying to shake hes hand, embrace him or pat him on the back.

"Here is a man from the Chinese community. He has something to say," said one gray-haired man to Shen, as the ctowd pressed forward and the ambassador began to make his way toward his departure gate at the other end of the airport.

"We the people here fully support the Republic of China forever," said the man from the Chinese community, Charles Wan, to the suddenly quiet crowd. Then, there was a cheer.

Several well-known American supporters of Taiwan were highly indignant when it appeared that no highlevel offcials from the State Department had shown up to extend the appropriate courtesy of a farewell to a departing ambassador. "I assume this must be by accident" said Washington attorney Thomas G. Corcoran to the crowd and the television cameras. "It would be very shabby if it were by desire."

As it turnedd out, under Secretary of State for Political Affairs David D. Newsom, who -- yesterday -- was the second highest ranking official in the State Department because Deputy Secretary of State Warren Christopher was on his way back from Taiwan, had been delayed by traffic as he headed out to the airport then drove directly to the airplane to pay his respects to Shen. But inside the airport there were speeches.

"I repesent Chinese Americans," said Anna Chennault "For the last two weeks I have felt very sorry for free people, but most sorry for the United States. But the people who are fighting for freedom will continue to fight. Fighting for freedom is a very lonely busness."

"Under the communist system there is no freedom," she said later. "We have to let the people understand what it means to be free. Taiwan is the fortress that ripresents freedom."

Stephen lo, first secretary of the Taiwan embassy here, came with his wife and child to the airport. "I came because he is my boss," Lo said, "I very respect him. I feel very upset. I don't want to talk anymore."

Four nuns, Sisters of Providence who run colleges here and in Taipei, also carried Nationalist Chinese flags. "He [Shen] he is a close friend," said Sister Donna Marie Fu. "We are very sad."

The mood for some was resignation. "What can we do?" said one man, shrugging his shoulders.

Several members of the Dingman family of Vienna, Va., came carrying placards, one of which said, "Send Carter to Red China, Keep Taiwan." Mark Dingman, 21, said he had become interested in Taiwan because his father is director of the Republican Study Committee.

"I'd like to make a statement," said his mother Ann W. Dingman, who was also carrying a placard. "I feel that President Carter has sabotaged the cause of freedom for the United States and for Taiwan just as effectively as if he were a paid agent of the Communists.

"I can stand here tlday and make that statement without fear of reprisal, and I wonder of the American people 15 years from now will enjoy that freedom. Think about that America!"