Widespread killing of female infants still may be practiced in China, and a specialist said the killings may number as high as tens of thousands a year, according to information released yesterday at the National Academy of Sciences.

The information comes from the first detailed reports of population statistics ever released by the Peoples Republic. The statistics also disclosed that about 27 million people died during the economic campaign, called the "Great Leap Forward," of the late 1950s and early 1960s.

After three decades of demographic secrecy about their huge population, the Chinese suddenly have disgorged a wealth of data in a special edition of the official Chinese demographic journal, "Population and Economics."

The issue, published late last year in China, reports details not only of the new 1982 census, the largest census in history by any nation, but also for the first time of the 1953 and 1964 censuses.

There are "dramas told by these data," said Ansley J. Coale, a Princeton University demographer who reported yesterday on the Chinese data for the National Research Council, the research arm of the National Academy of Sciences.

Striking achievements and disasters are reflected in the data, Coale said, including a public health program that has raised life expectancy far above what might be expected for a country with as little development as China.

Life expectancy is now 69 years for Chinese women and 66 for men, an increase of 20 years over the past three decades. At the same time, the fertility rate has been cut in half.

On the problem of female infanticide, Coale said the statistics show that overall the male-female ratio is near the norm of 106 boys to 100 girls at birth.

But the figures also show that, in rural areas, the ratio is 112 males to 100 females for third children at birth. Since about 1 million girls are born as third or later children, the discrepancy between the natural rate of 106 boys and the reported rate of 112 indicates a loss of about 60,000 baby girls a year.

For fourth children, ratios are even higher, 115 boys to 100 girls. In some regions of China ratios as high as 130 or more to 100 have been reported.

Coales said it is possible that some of the missing girls may be accounted for by the Chinese practice of not reporting to authorities the births of third or later children, especially girls, because of the government's strong sanctions against having more than one child.

Numerous stories in Chinese newspapers reporting and condemning infanticide, however, support the likelihood that a substantial portion of the distorted ratio is caused by infanticide.

The reports cite it as a serious problem remaining from the "feudal" past and describe in gory detail the means of killing baby girls, such as keeping a water bucket near the maternity bed in which to drown girls as soon as they are born.

Also, in the official Chinese journal, female infanticide is mentioned as one explanation of the unusual ratio.

The Chinese numbers also show a striking leap in the death rate in the years around 1960, coinciding with the "Great Leap Forward," the economic program of former Communist Party chairman Mao Zedong.

The death rate was just above 20 per 1,000 people in the mid-1950s. It leaped to 38 per thousand in 1960, and dropped to about 13 per thousand by 1963.

Coales said the rates meant that about 27 million people died who otherwise would not have if the death rates had remained steady.

"The peak in 1960 is without any doubt the result of the economic crisis that came during the Great Leap Forward," Coales said.

The economic scheme was one intended to modernize Chinese agriculture and industry at once. Mass changes were ordered in social and economic organization to achieve it.

The result, according to Coales, was that the Chinese "didn't properly collect and distribute the