Members of Congress accepted $4.5 million in speaking fees last year from special-interest groups, more than twice the 1980 figure of $2.2 million.

The speeches, many of them for the maximum allowable fee of $2,000, were made to a wide array of business, academic, medical, political and religious groups, from the Chemical Manufacturers Association and the Fertilizer Institute to Georgetown University and the American Heritage Foundation.

According to an analysis by the Democratic Study Group of congressional financial disclosure statements, the biggest gains were made by Republican senators. In 1980, their speaking income was $601,000. After winning additional seats that year and gaining control of the Senate and its chairmanships, they nearly tripled their speaking fees to $1.6 million in 1982.

The Senate has no limitation on outside earned income. In the House, members are limited to outside earnings of 30 percent of their salary, which in 1982 was $60,662 for most members, and must give anything above $18,200 to charity. (There is no limit on outside unearned income, including rents, dividends and interest.)

On the average, Senate members were much more in demand last year than House members. Speaking fees totaled $2.4 million for the 100-member Senate, compared with slightly less than $2.1 million for the 435-member House.

Eight Senators and 66 House members accepted no speaking fees. Six other senators and 10 House members contributed all of their fees to charity.

In the House, 11 Democrats and nine Republicans exceeded the 30 percent limit, earning between $18,200 and $51,898. They included five members of the House Republican and Democratic leadership, three Democratic committee chairmen, seven members of the Ways and Means Committee and three members of the Energy and Commerce Committee.

The top five earners were Rep. Dan Rostenkowski (D-Ill.), chairman of Ways and Means, $51,898; Rep. Jack Kemp (R-N.Y.), $42,880; Rep. Robert H. Michel (R-Ill.), the House Republican leader, $37,000; Rep. Guy Vander Jagt (R-Mich.), $36,550; and Rep. Henry A. Waxman (D-Calif.), chairman of the health and environment subcommittee, $33,425.

In the Senate, with no limit on speaking fees, 13 members received more than $50,000. They were led by Sen. Robert J. Dole (R-Kansas), chairman of the Finance Committee, who received $135,750 and gave $51,500 to charity; Sen. Ernest F. Hollings (D-S.C.), who accepted $92,270 and gave none to charity; and Sen. Pete V. Domenici (R-N.M.), chairman of the Budget Committee, who accepted $84,450 and gave $27,000 to charity.

When the House last year decided to retain the 30 percent limit on outside income, it raised the House salary to $69,800. The Senate decided to keep salaries at $60,662 with no cap on outside income.

The House this year voted to require the same 30 percent limit of senators. The Senate Appropriations Committee rejected the proposal yesterday.

The Democratic Study Group found that not all outside earned income was reported. The law requires only legislators in office May 15 to file a report for the preceding year. Thus, members who retire, resign or are defeated are not required to report income from their last year in office.

This year 83 former House members and five senators fall into that category. Projecting from the 1981 figures, the study estimates that they earned an additional $500,000 in outside income in 1982.