BEIJING, NOV. 24 -- Li Peng, a Soviet-trained engineer and adopted son of late premier Chou En-lai, was appointed China's acting premier today following the resignation of Zhao Ziyang from that post.

The standing committee of China's National People's Congress, the rubber-stamp legislature, approved the appointment of Li, 59, after Zhao became the party's general secretary, the country's highest position, at last month's party congress. The office of premier is considered the second most important post. Li was one of five vice premiers.

Li is virtually ensured of being officially named premier when the National People's Congress holds its annual session in March.

Li, whose appointment was expected, is seen as a compromise choice who was acceptable to a number of groups, including traditionalist party elders. Although Zhao and Li hold the two main leadership positions, control over China's general direction is said to remain in the hands of senior leader Deng Xiaoping, who retired from all but one of his official posts at the congress.

In a speech immediately after his appointment, Li declared that he would adhere to communist principles and the policy of "carrying out various reforms and opening to the outside world."

Li is regarded as a technocrat but some Chinese fear that he is conservative in his views and will slow down some of the country's most innovative economic reforms. In today's statement, Li said economic development should be "further stabilized," an indication to some observers of Li's cautious approach to reform.

Many intellectuals, including university students, are mistrustful of Li because they believe his rise to power has been based more on his personal connections with senior leaders than on his abilities and achievements.

Li's father was a "revolutionary martyr" who was captured by the Nationalist Chinese in 1930 and executed when Li was 3. The late premier Chou En-lai and his wife, who were childless, became Li's foster parents and, according to some accounts, raised him as if he were their own son.

His father's record and his connection with Chou gave Li Peng impeccable credentials and a network of friends among party elders.

Unlike the older leaders who fought in the war against the Japanese and Nationalist Chinese, Li has no battlefield experience.

At the same time, Li's no-nonsense dedication and technical expertise impress nearly everyone he meets. Witnesses said that Li worked on papers he had brought with him during the entire halftime break at a soccer game in 1984.

Born in Sichuan Province, Li joined the party in 1945 at age 17. He went in 1948 to the Moscow Power Institute, where he spent seven years and learned to speak Russian. After his return to China, Li held successive jobs in the power industry, one that has always emphasized central planning.

Westerners who have met Li do not consider his Soviet training a major obstacle to a continuation, or even a strengthening, of China's ties with the West. Many Chinese officials of his generation were trained in Moscow but favor strong ties with the West.

As a vice premier, Li has traveled widely, including a trip to the United States in the summer of 1985.

Western diplomats are divided in their view of Li's approach to economic reforms, and he remains an enigma to many foreigners despite his long bureaucratic career and numerous public appearances.

Some diplomats believe that Li, whom they describe as a "go slow" reformer, may some day come into conflict with reformist leaders such as Zhao, who advocate transforming the centrally planned economy into one more responsive to market forces.

In a recent book, Kenneth Lieberthal and Michel Oksenberg, China scholars at the University of Michigan, describe Li as a cautious reformer, noting that he "does not believe in the magic of the market place."

What seems clear is that Li was acceptable to some of the party elders who feared China's reformist leaders were changing the old system too rapidly. Chen Yun, 82, the senior economist who recently retired from the powerful Standing Committee of the Politburo, took an early interest in Li Peng and assisted him in his rise.

Unlike many other officials, such as Deng or Zhao, Li escaped persecution during the chaotic years of the Cultural Revolution from 1966 to 1976. According to Lieberthal and Oksenberg, this suggests that "he remained under the protection of powerful patrons," such as Chou En-lai.

A profile of Li released today by the official New China News Agency said that during this turbulent period, Li maintained a normal supply of electricity to the capital as director of the Beijing Electrical Power Adminstration.

In 1985, Li was made head of a newly established State Education Commission, but when student demonstrations erupted at the end of last year, Li took none of the blame.

Party Chief Hu Yaobang was ousted after being accused of weakness in dealing with the demonstrators, and Li joined in the criticism of Hu.

In March 1985, China sent Li to Moscow for the funeral of Soviet president Konstantin Chernenko. He became the first high-level Chinese official to meet with Soviet leader Mikhail Gorbachev after he assumed power.