China's Communist Party announced tonight sweeping changes in its leadership, structure and official history that appear to give 75-year-old Vice Chairman Deng Xiaoping one of the great triumphs of his career.

Through a communique issued at the end of a plenary session of the party Central Committee, Deng purged his worst remaining enemies on the ruling Politburo, promoted his closet protege to new power and fully restored the good name of his longtime ally, the late president Liu Shaoqi.

The rehabilitation of Liu was an extraordinary turnabout, requiring a complete revision of the official history of China's tumultuous Cultural Revolution and a new image for a man usually described 10 years ago as the worst villian ever to walk Tienanmen Square.

"It would be like the Americans bringing Nixon back to power," one diplomat here said.

The changes clearly tarnished the memory of the late chairman Mao Tse-tung, who had purged both Liu and Deng in 1966, and further limited the power of the man Mao anointed in 1976 as his successor, current party Chairman Hua Guofeng.

Deng's personal grip on the party was evident in the Central Committee's decision to endorse publicly his move to delete from the Chinese constitution a direct quote from Mao that had guaranteed Chinese citizens the right to "speak out freely, air their views fully, hold great debates and write big-character posters."

The change is expected to chill further China's small prodemocracy movement, although the constitution still supposedly guarantees freedoms such as speech, correspondence, the press and assembly.

Since his return to power in July 1977, Deng has gradully built up his strength in the party in cooperation with other veteran party officials who favor pragmatic economic development, more foreign trade and promotions and school admissions based on technical skill and grades rather than proper worker-peasant class background or fervant adherence to Mao's political thought.

But many local leaders appeared to be dragging their feet in making changes such as payment of large bonuses to their best workers. They feared Deng might die or suffer a political reversal that would put his adversaries -- some retaining their Politburo seats -- back in control.

Tonight's announcement by the Fifth Plenum of the 11th Central Committee seemed designed to remove all those doubts and ensure the continuation of the policies of Deng and his several aged colleagues long after their deaths. Deng presided over the seven-day plenary session.

The central Committee "approved the resignations of Comrades Wang Dongxing. Ji Dengkui, Wu De and Chen Xilian and decided to remove and propose to remove them from their leading party and state posts."

Wang was a former Mao bodyguard and until tonight ranked sixth in the party hierarchy, although his influence had clearly diminshed in the last year. p

Ji, a party technocrat, Wu, the former mayor of Peking, and Chen, the former Peking region military commander, appeared to be the three other Politburo members closest to Mao and least convinced by the need for Deng's pragmatic reforms. Another, apparently innocuous member of their group, model peasant Chen Yongsui, escaped the Politburo purge.

In place of Wang, the last man in the six-man standing committee that heads the party hierarchy, the Central Committee added two Deng proteges, Hu Yaobang and Zhao Ziyang.

Hu, perhaps Deng's closest associate in the party, was also given the even more critical post of general secretary of the newly restored party secretariat. The job has such strong historical echoes that it seems to all but name Hu as Deng's chosen successor.

Zhao, up to now the party chief in China's most populous province, Sichuan, reportedly has been brought to Peking to assume major responsibility for day-to-day work of the Chinese government, paralleling Hu's day-to-day party responsibilities as general secretary.

Hu, about 64, and Zhao, 61, represent a second generation of Chinese Communist leaders, groomed to take over from the men like Deng in their seventies and eighties who have run the country for the last 30 years. Their elevation raises questions about the future role of Hua Guofeng, Mao's chosen successor and the current holder of the top positions of party chairman, government premier and military commission chairman.

Hua, about 58, is even younger than Hu and Zhao. He has gained such prominence through a series of unusual overseas trips that his removal could prove embarrassing and politically difficult.

Hua has appeared content to serve so far as a front man for Deng's group, despite his lack of close personal and historical ties with them. The communique announced that a new party congress would be held before a 1982 deadline "in view of rapid changes in the domestic situation." Hua's status might be clarified then, or at a national people's congress scheduled for later this year.

Hu's promotion to general secretary of the party secretariat repeats almost to the last ideograph actions taken by the party committee in 1956, when Deng and Liu were in power. As such it is a blatant slap at Mao and assertion of Deng's personal influence.

In rehabilitating former president Liu, the party communique said it had decided to remove the labels of "renegade, traitor and scab" attached to Liu after his 1966 purge at the beginning of Mao's cultural Revolution.

"This was the biggest frame-up our party has ever known in its history and must be completely overturned," the communique said.

Mao, with the help of the them head of the Army. Lin Biao, launched an attack on Liu, Deng and other party veterans in 1966. Mao felt the party leadership was turning into a collection of uninspired technocrats wedded to their personal privileges and interested in motivating people only through capitalist-style material rewards rather than revolutionary fervor. Mao succeeded in removing thousands of top leaders, but left the government and economy in such turmoil that he reconsidered in the early 1970s, particularly after Lin allegedly tried to assassinate him. In 1973 Mao, urged on by then premier Chou Enlai, began to bring men such as Deng back into power.