The number of federal convictions for white-collar crime rose 18 percent in the first five years of the Reagan administration while convictions for other types of crime went up more than twice as fast, the government said in a report released yesterday.

The study, the first national survey of its kind issued by the Justice Department's Bureau of Justice Statistics, also found that white-collar criminals were less likely than other types of criminals to be sentenced to prison.

The bureau reported that 10,733 defendants were convicted of federal white-collar crimes in 1985, up about 1,600 from 1980. Meanwhile, federal convictions of non-white-collar crimes rose 43 percent from 1980 to 1985, to about 30,000.

The average length of a prison sentence for a white-collar criminal increased 20 percent to 29 months in 1985, compared with two years in 1980, the report concluded. The average length of a prison sentence for other types of federal criminals was 50 months in 1985, about the same as it had been five years earlier.

Tax-fraud convictions of organized-crime figures and drug dealers contributed to the trend of somewhat longer sentences for white-collar criminals. The study cited an 86 percent increase in the average length of prison sentences handed out to those convicted of tax fraud from 1980 to 1985, from 11 months to 21.

On the incarceration rate, the bureau found that 40 percent of convicted white-collar criminals were sentenced to prison in 1985, compared with 54 percent of the non-white-collar criminals. The rate for white-collar criminals in 1985 was about the same as in 1980.

Of the white-collar convictions two years ago, 55 percent were for fraud, 19 percent for forgery, 16 percent for embezzlement, 5 percent for counterfeiting and 5 percent for white-collar regulatory offenses.