A Justice Ministry spokesman said today that one of China's most prominent dissidents is in "good health," despite reports that he had been punished with solitary confinement for smuggling his memoirs out of prison.

The spokesman, who identified himself only as Zhang, answered questions submitted more than a week ago concerning reports reaching an exile organization that the dissident, Xu Wenli, had his rations reduced and was placed in solitary confinement. The reports also said Xu was denied exercise and family visits.

The reports reaching the New York-based Chinese Alliance for Democracy said Xu had been questioned repeatedly about how the manuscript was smuggled out of prison. His wife was quoted as saying that his health had deteriorated.

Xu Wenli was considered the most moderate of the leaders of China's ill-fated Democracy Movement of 1978-80. A railroad electrician who became an editor, he was given a 15-year prison sentence after being arrested in the spring of 1981 and later being charged with organizing a counterrevolutionary group and with counterrevolutionary propaganda and agitation.

In a lengthy memoir smuggled out of prison, Xu denied that he was guilty of such activities. He said he favored reform and not wholesale rejection of the Communist Party.

Xu has been consistently more moderate in his criticism of the party than were some other dissidents, such as Wei Jingsheng, a Democracy Movement writer sentenced to 15 years in prison for "counterrevolutionary crimes" in October 1979.

Responding by telephone to questions that had been submitted in advance, the Justice Ministry spokesman said, "Xu Wenli violated the laws of China and is now serving a prison term in a prison in Peking."

"It is not our task to give detailed accounts of the circumstances of prisoners in custody," the spokesman said, but he added, "China has consistently insisted on a policy of reforming prisoners and giving them humanitarian treatment."

"Even for those prisoners who violate prison regulations, there is no reduction of their allowances of food, clothing and daily necessities," the spokesman said. "As far as we know, Xu Wenli is in good health."

The spokesman did not address the question of whether Xu had been placed in solitary confinement or denied family visits.

In a 1984 report, Amnesty International, the London-based human rights organization, said that the Chinese authorities had not replied to several inquiries it had made about Xu.

The Justice Ministry rarely comments on the conditions under which individual prisoners are held. At a meeting with reporters yesterday, Public Security Minister Ruan Chongwu said he knew nothing about how Xu was being treated or about Wei Jingsheng.

Ruan said that only foreigners are interested in the case of Wei, who is the most prominent jailed dissident.

Ruan said that "not one" prisoner is being held in China for his political views.

Meanwhile, Zhu Jianming, former vice minister of justice, told Agence France-Presse yesterday that as of the end of last year, Wei Jingsheng was in good health.

Information about Wei has been scarce since he was imprisoned seven years ago.