The world's smallest Communist country, Albania, has told the world's largest Communist country, China, to get out.

After 16 years of "unbreakable friendship," during which it received millions of dollars in Chinese aid, the Albanian government told the Chinese embassy in Tirana that the Chinese experts working there should leave as soon as their contracts expire, diplomatic sources here say.

The Chinese already appear to be leaving Albania, Europe's most isolated country. Once thought to number more than 7,000, they are now believed by observers in Tirana, the Albanian capital, to be down to not more than 2,000 and perhaps few as 700.

They are seen much less frequently than before in hotels, restaurants and holiday resorts in the beautiful, mountainous country wedged between Yugoslavia and Greece.

Some Chinese interpreters studying Albanian are said to have told other foreign students that they will soon be going back to China for good.There has been a similar exodus of Albanian students from Peking.

The first clear sign of a break between Tirana and Peking was given in a 10,000-word editorial in Albania's Communist Party newspaper Zeri I Popullit earlier this month. The editorial, grandly entitled, "The Theory and Practice of the Revolution," branded China's new, more flexible policies as "opportunist" and "anti-Marxist."

There is little doubt that the article was intended to signal a major political event in Albania. Full translations in English, French and German were rushed by special courier from Tirana to Albanian embassies abroad, including those in Belgrade and Peking. Radio Tirana suspended its normal programs for three days to broadcast extracts.

Travelers report seeing piles of reprints in hotels and restaurants throughout the country.

Western diplomats who have visited Albania recently say the present dispute with China, which bears some similarities to the quarrel between Albania and the Soviet Union in 1961, has long been brewing beneath the surface. Albanian disenchantment with China can be dated from the silent disapproval given to former President Nixon's first visit to Peking in 1972. More recently, the Alabanians have been disappointed as the purge of the radical "Gang of Four" and the rehabilitation of the moderate Teng Hsiao-ping.

The growing strains in Sino-Albanian relations can be charted by appearances of the Chinese ambassador at the annual May Day parade in Tirana. In 1975, he was seen alongside Albanian leader Enver Hoxha and other government officials. By 1976, he had been downgraded to the foreign diplomats' stnd. This year, he was said to be "suck" in Peking.

During its militantly isolationist period. Faraway China was undoubtedly a valuable ally for Albama. It provided much-needed assistance for Albania's struggling economy and bolestered the country's sense of independence from its bigger Balkan neighbors. Decendants of the ancient Illyrians, the Albanians have long been proud of their separate nationhood in a country of 2.5 million.

Opening up to the outside world, however, has entirely different implications for the two Communist states. With 300 times the land surface and nearly 400 times as many people as Albania, China runs little risk of being contaminated by foreign ideas. So Albanian leaders are projecting their country as the one remaining center of true revolution.

Daily newscasts from Radio Tirana depict Albania as a workers' and peasants' paradise that is the object of unbounded admiration by all progressive and right-thinking people. Reports from the few Western visitors allowed to penetrate the citadel of true Marxist-Leninism paint a different picture.

For the last 30 years, Albania has been preserved as a political museum by Hoxha, 68, who has the distinction of being the world's only remaining disciple of Joseph Stalin still in power. The late Soviet dictator peers from Albania's postage stamps, presides in effigy over Tirana's main streets and has given his name to dozens of factories and collective farms.

His protege, Hoxha, despite receiving much of his education in France and Belgium, is probably the most ant-western of Communist leaders. He and his Italian-educated premier, Mehmet Shehu, have devoted their career to maintaining a strict isolation.

They have been quite successful all hints of Western influence are rigorusly suppressed. Long hair, blue jeans, pop music - signs of mild protest by young people in other Eastern European countries - are totally absent in Albania.

Apart from a handful of diplomats and senior officials, travel to Western countries is impossible. Foreign books and films are banned and even Yugoslav television is jammed.

The few Albanian officials allowed to have dealings with foreigners are constantly rotated - apparently to prevent them from building up close relations. A foreign businessman who makes frequent trips to Tirana remarked that he never sees the same official twice.

Officials are now also apparently forbidden from accepting the smallest gift from a foreigner - even in a five-cent tip or a ball point pen. "A few years ago, I used to be able to give my Albanian counterpart a bottle of whisky as a present. Now he won't accept anything," says the businessman, who prefers to be anonymous for fear of jeopardizing his interests in Albania.

Albanians who live abroad (there is a large Alabanian minority in Yugoslavia) are allowed to maked occasional trips back to Albania - but cannot visit their relatives in their homes. Family reunions take place in the Dajti Hotel, which is reserved for foreigners, and are strictly supervised.

The one, rather surprising concession to Western influence is the nightly rebroadcasting of Italian television news. The screens go blank, however, any time there is an item about the Pope, since Albania proudly proclaims that it is the world's leading athelist state.

For ordinary Albanians, with little knowledge of the outside world, life has slowly been improving since the Communists came to power after World War II. Goods in the shops may seem incredibly primitive compared to Western or even Eastern European standards - but represent an improvement on what was there before.

Foreign diplomats are largely restricted to their embassies, each other's homes, and the Dajti Hotel, which boasts the one nightclub in town. Interest centers on the hotel band's accordion player (long rumored to be the chief agent of the secret police) and a buxom Polish dancer who appears on Saturday nights.

On Sundays, most of the diplomatic corps drive across the Yugoslav border to Titograd in search of relaxation.