The share of U.S. taxes paid by American corporations continued to decline last year as the business tax burden dropped to 6.2 percent from 12.5 percent in 1980, according to a study released yesterday by the Joint Committee on Taxation.

The amount of federal income tax that corporations pay as a proportion of their revenue -- the effective rate -- also has declined, contributing to the reduced share of corporate taxes to total federal receipts, the study said. The effective tax rate on U.S. income declined from 21.8 percent in 1980 to 17.2 percent in 1981 and 16.1 percent in 1982, the study said. In 1983 it was 16.7 percent.

A tax reform proposal released this week by the Treasury Department would attempt to boost corporations' effective tax rates and federal tax burden while reducing that for individuals. Under the Treasury proposal, federal tax receipts from corporations would increase 30 percent in fiscal 1987 and grow by as much as 36 percent by 1990.

"This continued shrinkage in corporate America's relative tax burden thrusts the vast majority of responsibility for the operation of the federal government on the individual taxpayer," said Rep. Don J. Pease (D-Ohio), who released the study. "From the viewpoint of economic efficiency, the reduction in corporate tax receipts aggravates federal budget deficits and the variation in effective tax rates distorts the treatment of industry sectors under the code."

"While many American working families who struggle with moderate incomes pay a significant amount of income taxes, in this study we discover that there are some industries and many individual corporations making hundreds of millions of dollars in profits and paying little or no income taxes," said Rep. Byron L. Dorgan (D-N.D.).

Pease joined a number of prominent economists and citizen tax groups in endorsing the Treasury plan because it shifts some of the burden of paying the federal budget from individuals to corporations.

According to the congressional study, between 1980 and 1983 the industries with the highest average effective U.S. tax rates were trucking, 38.2 percent; tobacco, 33.3 percent; pharmaceuticals, 32.9 percent; instrument companies and food processors, both 29.5 percent, and computers and office equipment, 25.8 percent.

The lowest rates were paid by railroads, 2.4 percent; chemicals, 3.6 percent, and financial institutions, 3.8 percent. Other industries with low tax rates in 1983 for which four-year averages were not available were construction, 0.7 percent; motor vehicles, 3.5 percent, and telecommunications, 4.8 percent.

The figures for share of federal taxes paid by corporations does not include the Social Security and excise taxes corporations pay.

While corporate taxes as a proportion of federal revenue have declined steadily from 32.1 percent in 1952 to 6.2 percent last year, individual taxpayers' share increased from 39.9 percent in 1950 to 48.1 percent in 1983, the study said.

The report covered 218 companies selected from the Fortune 500 Industrials and Fortune Service 500 lists.