A day before U.S. Commerce Secretary Malcolm Baldrige is due to arrive here to help untangle Sino-American trade snags, Chinese authorities summoned the U.S. ambassador to raise an issue that threatens air links between the two countries.

Western diplomats said the Chinese Foreign Ministry called in Ambassador Arthur Hummel Jr. to protest Washington's recent decision allowing Pan American World Airways to resume flights to Taiwan. U.S. Embassy officials refused to give details.

Diplomats said the protest seemed timed to put Baldrige on the defensive even before his arrival with a trade mission aimed at expanding U.S. commercial dealings with China. Peking often has used such tactics to extract greater concessions during coming talks.

Baldrige faces a series of trade disputes that blemish a generally rosy commercial relationship. In addition to the airline issue, Peking has hotly protested U.S. import quotas on Chinese textiles and delays in approving sales of high technology.

The airline issue erupted last month after the Reagan administration approved Pan Am's plans to reactivate its service to Taiwan June 14. Pan American, the only U.S. carrier serving the Chinese mainland, halted its Taipei route in 1978 in the hope of getting more lucrative business to China.

The financially strapped airline operated at a loss in its China operations last year, flying with an average of 30 percent capacity. Pan Am Officials said the airline decided to resume Taiwan service three times weekly for "economic" reasons.

But Peking considers it political betrayal for Pan Am to reestablish air ties to the capital of the rival Chinese regime. In a letter to the U.S. Civil Aeronautics Board, Peking threatened "severe repercussions" if the Taipei flights resume.

The precise meaning of the threat is unclear, but if Peking withdraws Pan Am's landing rights in China, Washington is expected to reciprocate by stopping flights to the United States by China's flag carrier.

Diplomats believe China will stop short of such drastic measures out of self-interest. An interruption of air service to and from the United States would impair commercial contacts Peking deems essential for its modernization. It also would cut the lucrative flow of American tourists to China.

Some analysts, however, predict China will put principle above profit in a case involving its sovereignty. They note that China banned the Dutch airline KLM from using Canton as an alternative or bad-weather airport when KLM resumed its direct air services to Taiwan in April.

Baldrige, who will be here for five days for the first meeting of the U.S.-China Joint Commission on Commerce and Trade, is the highest administration official to visit China since Peking broke official cultural and sports ties following America's granting of political asylum to Chinese tennis star Hu Na.

As a result of the Hu incident and U.S. arms sales to Taiwan, political relations between Washington and Peking are said to be at their lowest point since establishment of diplomatic ties in 1979.