China's Communist Party tonight named reformer Hu Yaobang as its new chairman, heading a list of sweeping leadership changes that cast aside the last vestige of the Maoist era and decisively strengthened the control of Deng Xiaoping and his pragmatic allies who are now running the nation.

Hua Guofeng, the man Mao Tsetung hand-picked as his successor in 1976, was demoted from party chief to junior vice chairman. He also was criticized by the Central Committee for opposing the pragmatists' reform measures that stress economic gains instead of the Maoist ideal of political activism.

Along with the long-awaited document criticizing Mao that the Central Committee has adopted but not yet released, Hua's demotion is seen as an attempt by the party to bury the Maoist period once and for all and get on with modernizing the world's most populous nation.

The elevation of Hu from party general secretary represents a significant victory for the party's moderate wing headed by Deng has moved with chess-like precision over the past three years to install his proteges in top party and government posts.

With his longtime friend Hu in the top party post, Deng has managed to complete his goal of placing men cast in his own mold -- energetic, flexible modernizers -- in the nation's top jobs and eliminating or neutralizing officials who prospered during Mao's disastrous Cultural Revolution.

Another Deng favorite, Zhao Ziyang, who replaced Hua last fall as the premier who runs the government, was named vice chairman, further strenghtening Deng's control of the party. Ranked ahead of Hua in the party hierarchy, Zhao is positioned to dilute Hua's influence as vice chairman.

Deng himself was appointed head of the party's military commission, which directs China's powerful armed forces. With Hu running the party and Zhao in charge of the state bureaucracy, Deng, an old Army political commissar, placed himself in a position to assure control of the military.

Hu, 67, and Zhao, 62, represent a new generation of communist leaders groomed to take over for men like Deng in their 70s and 80s who have been running the nation for 32 years. Deng, 76, who holds formal title of party vice chairman despite his political dominance, views both men as trusted successors.

The political partnership of Deng and Hu began 40 years ago, not long after Hu left his native Hunan Province to become a "little red devil" or child soldier fighting for communist forces. Since the two men fought side by side against the Japanese in the arid Taihang mountains of northwest China, Hu has shared his senior partner's political ups and downs.

In 1952, Hu followed Deng to Peking, where he began his long career as head of the Communist Youth League, the main avenue of entry into the party for most of the second generation of communist leaders.

The two men disappeared in 1966 after Red Guards criticized them for, among other things, directing private railway cars and special airplaines to ferry bridge partners across the country, where they allegedly would pursue their obsession with card games during working hours.

When Deng briefly regained power in 1973, he assigned his old friend to the battered Academy of Sciences. And when Deng was purged again in 1976, Hu also vanished, until his mentor again reappeared in 1977 and had his old lieutenant placed on the party Central Committee.

Today's leadership changes, announced through a communique issued at the end of a week-long Central Committee meeting in Peking, were described as measures "to strenghten the Central Committee's collective leadership" and assure implementation of the far-reaching reforms put forth by the Deng faction.

Since regaining power in 1977, Deng ahs fashioned a package of controversial measures, including the use of material incentives to spur productivity, cutting the defense budget in favor of investment in comsumer industry, giving workers greater say in running their factories, resumption of competitive examinations as criteria for higher education and an opening to the West to help China modernize its creaky economy.

Many of the policies have been resisted by officials at the lower levels of the party, who feel personally threatened by the reforms and disagree with the philosophy behind them. This problem is exacerbated by the fact that nearly half of the party's 38 million members joined during the tumultuous decade of the Cultural Revolution when political purity, not competence, was the entry criterion.

Frustrated with this resistance, Deng supporters have criticized Hua, a Mao disciple who was appointed premier and party chairman during the Cultural Revolution, for serving as a rally point for the remaining Maoists in the party and for disgruntled military officers who objected to the defense budget cuts, according to Chinese sources.

Hua, who had become increasingly isolated since Deng's return in 1977, had given ammunition to his critics by restating such Maoist principles as spiritual incentives at a meeting of military officers in April 1980 and by publicly criticizing the restoration of private plots in the countryside and bonuses in the cities as way of improving worker output.

According to a commentary issued by the official New China News Agency, the Central Committee censured Hua for commiting "left" errors, including his efforts to counter Deng's view that science and technology, but political activism, should be the basis for national policy.

"Criticism of Hua Guofeng had come from many party members since last August," said the commentary. "They pointed out that Hua was no longer fit for party chairmanship."

Although the commentary and communique said that Hua had offered his resignation, sources report that his departure resulted from a carefully orchestrated series of moves by Deng dating back to last fall when he began trying to form a consensus on the criticism of Mao and to plan the ouster of Hua.

Hus offered at the time to step down in exchange for an agreement not to be implicated in the trial of the redical Gang of Four, sources said. Hua was minister of public security during the brutal suppression of demonstrations at Tiananmen Square in April 1976.

The deal to move aside Hua, however, collapsed in December when military officers and leftist party leaders objected to the highly detailed and harsh criticism of Mao then circulating in draft form, according to sources. Hua became viewed as a guardian of the Maoist legacy.

The leftists and military conservatives staged a counterattack at a Politburo work conference.

Deng blunted the attack by moving to the left himself, and again moved to replace Hua.

Allowing Hua to gain the poistion of vice chairman appears to have been a compromise, lowering his a few notches to make way for Hu but still allowing Hua to have a voice in matters of state.

The New China News Agency commentary applauded this as a form of "inner-party democracy," an alternative to "using a club against erring comrades."