China's public health minister has told U.S. officials that Peking is giving "active and urgent consideration" to a processing center inside China for refugees from Vietnam.

U.S. Health, Education and Welfare Secretary Joseph A. Califano, who met twice here with Public Health Minister Qian Xinzhonu, said today that this appeared to be the most positive response so far to the idea from the Chinese.

The U.N.-proposed center in southern China would help absorb the massive flow of boat-borne refugees and give them convenient access to Chinese-speaking health and relief officials. Most of the refugees are ethnic Chinese.

Califano said Qian "also expressed the hope that United States and China could go to the United Nations with a solid and unified position on refugees" before a planned U.N. conference on the problem beginning July 20.

Diplomats cautioned that it was not certain that the Chinese would eventually agree to a center. There has also been little discussion of how many refugees they would actually agree to house, even temporarily, before their reassignment to Western countries.

Yet the diplomats added that the Chinese had clearly begun to take the plan more seriously in light of the growing magnitude of the problem and President Carter's announcement that the United States would double the number of refugees it would receive.

Vice Premier Li Xiannian told Califano Sunday before the secretary left Peking that China had its hands full with 230,000 ethnic Chinese refugees. Most of them are now living in southern China after crossing the border from Vietnam in the last two years.

"We have a very large population," Li added. "We have enough people already. We have 900 million people, 900 million."

Califano said Li had offered to consider the center proposal, which U.S. officials have strongly supported, in "vague terms." He said the Chinese set no deadline for their decision in his most recent talks with Jiang, "but its clearly on the front burner."

Califano and other U.S. officials have emphasized in talks with the Chinese that funds from other countries including the United States, would pay for the processing center. Those countries are now contributing to the support of refugees in increasingly cramped and unhealthy quarters in Hong Kong, Malaysia and other current refugee destinations.

"The Chinese have made it clear that one of the things they would need is some resources to do things like this, although they could provide Health personnel," Califano said.

China attacked Vietnam in a brief border war earlier this year, in part because of Hanoi's efforts to expel all its ethnic Chinese and forge an alliance with the Soviet Union. Califano said that the Chinese "may be somewhat more emotional than we are [about the refugees] but I don't think their feelings are any stronger than ours about the brutality involved here."

The Chinese have supported the idea of an international conference on the problem. They have called for worldwide criticism of Vietnam for encouraging the refugees to leave Vietnam on frague boats and charging them $500 to $4,000 apiece for the privilege.

The official Chinese press has indicated in recent months that Ethnic Chinese are still crossing the border from Vietnam into China, but not in nearly the numbers that flooded southern China last year. Peking says most of those Chinese have been placed on farms organized in the 1950s for overseas Chinese. They grow hemp, tea, and various fruits and vegetables. It is hot and difficult work for which the emigrants are paid very little.

Refugees reaching Hong Kong say many Chinese from Vietnam now in south China would like to move to Hong Kong or the United States. Reportedly some with relatives abroad have been allowed to do so. CAPTION: Picture, Refugees swarm onto Hong Kong territory after cutting the anchors of their ship and letting it drift to land. AP