The inmates of Peking's municipal prison are now required to study the same political philosophy that landed millions of Chinese in jail only a few years ago.

Every night when the heavy lead cellblock doors shut behind them, they pore over a Communist Party document that vilifies the Cultural Revolution and portrays Mao Tse-tung as a flawed leader.

"Some people were thrown into prison just for damaging Chairman Mao's portrait," said deputy warden Xing Zhonghe, describing the old days. "We really didn't understand the Cultural Revolution. We thought it was carrying out revolution under Mao's banner. Now we understand what it was. The Central Committee has given us a very good analysis. It takes time for everybody to accept the real truth."

For Chinese prisoners, accepting "the real truth"--the prevailing political ideology--can be the key to freedom. Penology in China is based on ideological remodeling, and inmates undergo intense indoctrination to "reform" their thinking so they can become productive members of society.

Communist prisons and penal farms have been filled over the years with people who violated "the real truth" and were branded as "counterrevolutionaries." In recent years, however, "the real truth" has become a moving target requiring awkward adjustments in places like Peking municipal prison, where political verities are magnified for a captive audience.

With its emphasis on "education" and prisoner welfare, the fortresslike jail in south Peking lives up to its reputation as China's showcase prison where foreign visitors are taken in hopes of dispelling their suspicions of the Chinese penal system.

Despite its high walls strung with electrified barbed wire, the prison seems like a country club compared with descriptions of rural labor camps, where it has been estimated that more than 80 percent of Chinese prisoners are assigned. Guards here carry no guns. Prisoners have access to a 50-bed hospital. They enjoy a well-balanced diet and have recreational time after an eight-hour shift in the facility's plastic sandal- or sock-making factories.

Then there is prisoner "education." During the Cultural Revolution of 1966 through 1976, prison officials drilled inmates in Mao's radical precepts. Prisoners showed signs of "reform" by parroting Mao's call to smash "old ideas, old culture, old customs and old habits of the exploiting class."

Xing said as many as 70 percent of the prison's several thousand inmates during the chaotic decade were charged as "counterrevolutionaries," a catchall for intellectuals, artists and moderate party veterans who opposed Mao's theory of permanent revolution.

Most of them--Xing refused to say exactly how many--were released in 1978 and 1979 after Deng Xiaoping and his team of pragmatists seized power and began to rid China of Maoist radicalism.

Xing was asked in an interview at the prison how people who had Maoism literally beaten into them could be expected to assimilate new political values.

"Through political study," he replied. "It wasn't only the prisoners. We also followed Mao's guiding thought to make revolution. We all need to do political study."

Mao's victims since have been replaced at the prison with a new class of "counterrevolutionaries" charged with plotting to undermine the current government. Xing said about 3 percent of the facility's 1,900 inmates have committed "counterrevolutionary crimes."

For this latest batch of political criminals as well as for common criminals who straddle the different eras, "reform" means mastering a new set of principles.

Since last summer, prisoners have been inculcated with the virtues of a Central Committee resolution that endorses Deng's moderate policies while describing the Cultural Revolution as a disaster and holding Mao responsible for it. Long-term prisoners once bombarded with Maoist truths have had to reverse their thinking.

The indoctrination process described by Xing features the Chinese penal techniques that some foreign critics consider a form of psychological coercion: force-feeding of political lessons, compulsory self-confession, peer pressure, individual criticism by warders and a skillfully manipulated system of rewards and punishment.

For two hours every night, the inmates break into "study groups" of 10 persons and hold ideological work sessions in the vaultlike, 12-by-15 foot cells where they also eat all their meals and sleep side-by-side on wooden platforms covered by straw matting.

In the sessions, they read aloud portions of the Central Committee document, passages from the party newspaper People's Daily or recent political speeches. Each inmate is supposed to explain how the lessons point out the errors of his ways.

Once a week, inmates are encouraged to turn on each other in "criticism and self-criticism" meetings. A prisoner first evaluates himself and then invites analysis from his cellmates.

The group encounters are augmented by individual sessions with prison officials who "point out problems" to inmates while never physically assaulting them, according to Xing.

Each inmate's progress is assessed in an annual review where warders reward good behavior with small cash bonuses and sometimes reduced sentences. The rebellious and recalcitrant are punished with stints in solitary confinement.

A wall in the women's cellblock holds up several recent essay exams asking such questions as: "What are the advantages of the socialist system compared to the corruption of capitalism?"

"We do everything possible to educate the criminals," said Xing. "We try to help them discard their past and turn over a new leaf."

Most Chinese prisoners are warehoused in the vast network of remote labor camps where criminal personalities and political outlook are reshaped through hard work, not ideological study. Survivors released in recent years say the food is scarce, work days very long and punishment often cruel. Labor camp internees can be sent away by the Public Security Bureau without trial or formal filing of charges.

By contrast, everyone at Peking's municipal prison has been convicted of a crime, and treatment there is comparatively benevolent. As one possible result, few try to escape.

"Our policy is reform first, labor second," said Xing. "Some prisoners who have reformed their thought have even decided they don't want to leave."