Departing from normal protocol, the Chinese minister of metallurgical industry, Tang Ke, rose at a recent banquet for visiting officials of U.S. Steel Corp. and declared that a Ronald Reagan presidency would be disastrous for Sino-American relations.

Despite that unusual outburst and what seems to be a general preferennce for President Carter, most Chinese show little appreciation for the differences between the two main U.S. presidential candidates.

When the official New China News Agency published an election analysis last week, it concluded that the campaign "has been indistinct to many Americans and even puzzling to a lot of foreigners as to what the candidates are debating" and what the "real points at issue" are.

Although that analysis may reflect accurately official and popular views of the campaign, it obscures what appears to be favorable personal sentiment for Carter, the U.S. president who set up full diplomatic relations with Peking after 30 years, and a general wariness of Reagan, the candidate who dared to rub against the sensitive Taiwan issue.

Reduced to traditional Chinese terms, Peking seems to feel more comfortable with the "foreign devil" it knows than the foreign devil it does not know, but it appears willing to deal with either.

"The Chinese say the Carter administration is known to them and they made progress with it," said a Western diplomat who regularly speaks to Chinese officials. "There's reasoned pessimism about Reagan because he's picked aides who are friendly to Taiwan. But nobody's hysterical."

The Chinese were less evenhanded in their political analysis several weeks ago when Reagan was calling for the establishment of "official" or "government-to-government" relations with the Nationalists on Taiwan.

Outraged that he would call for official contacts with the island government just two years after they were downgraded as a precondition for full relations with the mainland, the Chinese attacked Reagan in the official press and gave an icy reception to his running mate, George Bush, when he visited Peking in August.

As the American political season ripened, however, so has China's view of Reagan. Reassured by his public backing off of earlier statements on Taiwan and private American predictions that he would not be willing or able to alter U.S.-Taiwanese relations if elected, the Chinese tempered their attacks on the Republican nominee.

In fact, the day after Tang Ke issued his warning to the U.S. Steel executives, China's chief America-watcher, Han Xu, told U.S. Ambassador Leonard Woodcock, according to sources, "Minister Tang really spoke out of turn the other night, didn't he?"

Publicly, Peking gloats that Reagan was forced to abandon his support for official U.S.-Taiwanese relations because of crtitism in the United States. "Embarrassed by the situation, he has not touched upon the issue recently," observed the New China News Agency in its election roundup last week.

In private, Chinese Foreign Ministry officials express confidence that a politician with such a long and staunch anti-Soviet record would hesitate to break ties with Peking for fear of losing bargaining power against the Soviets, diplomats here say.