Foreign ministers of the European Common Market gave quick and unanimous approval today for talks with China about a historic trade pact.

Negotiations are expected to open here before Christmas. An agreement would link over a billion people, or almost one-third of all mankind.

An accord would be the Common Market's first with a Communist country. Today's decision is seen here as a slap in the face for the Soviet Union, which has angered Market officials by its reluctance to extend full diplomatic recognition to the European Economic Community and which is also embroiled in sharp disputes with several member countries, particularly France and Britain, over fishing rights.

No such quarrels exist with Peking China apparently regards its gradually developing relations with a united Western Europe as a cornerstone in its policy of opposition to the international dominance of the two superpowers, the United States and particularly the Soviet Union.

Evidence of a pro-Europe bias in Peking's policy came "in a sudden spurt" earlier this year, say Market officials. Then, in July, an EEC delegation left the Chinese capital convinced that China's new leadership wanted to reach agreement quickly with the nine-member Common Market.

Key points in the proposal made today by the foreign ministers - who are also moving with uncharacteristic speed - are an easing of import quotas and lifting of trade restrictions against Chinese Goods. In return, the Community is seeking greater entry to China's potentially large market.

China is expected to stress a more balanced trade relationship with Western Europe. China purchased $1.1 billion worth of EEC goods in 1976 but sold only $832 million, largely in the form of foodstuffs, textiles and raw materials.

The EEC's trade surplus could easily swell if Peking embarks on a shopping spree for Western technology as Sinologists here expect.

A pact between China and the Common Market could be a pace-setter for ties with East European countries, EEC officials say. They think the Eastern European states have shunned-in-depth trade ties in response to Soviet pressure for collective, bloc-to-bloc bargaining.

Moscow wants to boost commercial links with Western Europe via Comecon, the economic organization of the Warsaw Pact countries, but Market officials in Brussels, fearing that dealing with Comecon will mean a tightening of the Soviet grip over Eastern Europeans, have so far only proposed a token accord.

An agreement with Peking, EEC sources say, would further undermine the Eastern Europeans' policy of not recognizing the Common Market, a position that appears to be collapsing."

Western Europe's move toward China dovetails with Peking's opposition to a superpower dominance and its contunuing feud with the Soviet Union. Those themes were bluntly restate by Chinese Communist Party Chairman Hua Kua-feng in a speech to the party congress in August.

"The Soviet Union and the United States are the hearthstones of the next world war," Hua said, calling "Soviet social-imperialism the more dangerous." Hua described Europe as "the keypoint of Soviet-American rivalry," a contest he termed a threat to world peace.

Like the late party Chairman Mao Tse-tung, the new Chinese leadership has strongly pushed the theory of the "three worlds" with the superpowers and the poor countries of the "Third World" at the two extremes and the middle ground occupied by a "Second World," materially rich but politically oppressed by Moscow and Washington. "We support the countries of the Second World, such as the European states and Japan in their struggle against the hegemony of the superpowers," Hua said in August.