China's crime rate has declined to one of the lowest in the world, according to government statistics. But, at the same time, Chinese officials express concern over an increase in juvenile delinquency.

Several weeks ago, the overseas edition of the official People's Daily said the number of crimes committed by persons under 18 had risen in the first quarter of 1985 to 36.1 percent of the total number of criminal cases. The paper quoted a spokesman for the Ministry of Justice as saying that juvenile delinquents are committing crimes at earlier ages and that this has become a problem of wide social concern.

At the end of last month, China's new minister of public security, Ruan Chongwu, said that despite a steady decline in the overall crime rate, the number of serious crimes rose 26.8 percent in the first nine months of this year compared with the same period last year. Much of this leap could be attributed to an increase in serious cases of theft, Ruan said. And, he added, 70 percent of the criminals were under the age of 18

Although no systematic study of the causes of juvenile crime is available, Chinese publications have pointed to a variety of causes, including poor education and family environment and the influence of "bourgeois ideas" that presumably entered China after it opened up to foreign trade and investment.

Some Chinese publications have even mentioned as a possible cause of juvenile crime the problem of unemployment, which is usually a taboo subject in China. Official publications usually decline to acknowledge that unemployment is a problem. When they do touch on the subject, they usually refer to it euphemistically as "waiting for employment."

The deans of several American law schools who visited a Shanghai prison recently were told by court officials that one of the reasons for crime in recent years has been a loosening of discipline and controls when rural and urban economic reforms were initiated. The Americans noticed during their prison visit that most of the inmates appeared to be young, many of them only about 19 or 20 years old.

An official legal journal called Law and Life, written for lay readers, said this year that young people engaging in crime were often "ideologically unstable."

Another issue of the same magazine gave as causes of criminal activity the influence of the Cultural Revolution, improper family education and the "corrosive influence of decadent bourgeois ideas."

The magazine said one major problem was that some young students were abandoning their studies and drifting from place to place.

"Some dropouts cannot find jobs . . . so they spend the whole day going around the city, watching movies and hanging around in shops and restaurants," the magazine said. "These activities undoubtedly form the breeding ground for taking the path of criminality."

The same journal said that a proposal had been made to amend the penal code to lower the age of criminal responsibility from 18 to 12 or 13.

Public Security Minister Ruan said recently that during the 22 months ending in June 1985, the overall number of criminal cases dropped 36.4 percent to 750,000.

A spokesman for the ministry said at a press conference in November 1984 that one reason for the drop in the crime rate was executions of criminals convicted of serious crimes.

In August and early September, at least 14 persons were executed in the Peking area. The majority of those executed were described as workers or peasants, most of them in their twenties, according to posters that were put up to announce the executions.