Donald L. Dotson, one of the most controversial chairmen in the 52-year history of the National Labor Relations Board, will join the Washington office of a Chicago law firm when his term expires next week.

Keck, Mahir & Cate, a firm that represents several large corporations in employment and labor law issues, announced yesterday that Dotson will join it as a partner when his term expires Dec. 16.

Dotson was a labor lawyer for Western Electric Co., Wheeling-Pittsburgh Steel Corp. and the Westinghouse Corp. before joining the Reagan administration in 1981 as an assistant labor secretary.

During his four-year tenure as NLRB chairman, the agency reversed several pro-labor policies adopted under previous administrations, prompting AFL-CIO President Lane Kirkland to suggest that unions should "return to the law of the jungle" rather than take their cases before the board.

Among them were rulings that allowed managers to question workers about union activities, that restricted the ability of unions to discipline members who work during strikes and that allowed employers to unilaterally shift work from union to nonunion plants in order to pay lower wages.

Dotson said his aim as the agency's chairman was to "return the board to middle ground" from what he said were pro-union decisions under the Carter administration and "reduce government interference in the collective bargaining process."

Unions so opposed Dotson that Jackie Presser, president of the 1.6 million-member International Brotherhood of Teamsters, suggested in 1984 that his union's endorsement of Reagan's reelection that year was contingent upon Reagan firing Dotson.

The Teamsters, the only major union to endorse Reagan's election in 1980, ultimately endorsed his reelection even though Reagan said he had no intention of firing Dotson.

Presser said later that he regretted publicly linking his union's presidential endorsement to Dotson's ouster, stating, "I've done the opposite of what I wanted."

But since 1985 Dotson has found himself in the dissenting minority in dozens of decisions by the five-member board, all of them also Reagan appointees.

For example, the board is considering regulations that would make it easier for unions to organize health care workers, one of the fastest growing segments of the labor force.

The proposed regulations would reverse a decision by Dotson that gave hospitals and other health care institutions wide latitude in determining the appropriate "bargaining unit" as a way of defeating unions in representation elections.

Administration and congressional officials said Dotson originally had wanted reappointment to another five-year term. However, with Democrats regaining control of the Senate in the 1986 election, Dotson's ability to win Senate confirmation was considered unlikely, they said.

Reagan has not named a replacement for Dotson. But administration sources said the president is expected to designate either James M. Stephens or Wilford W. Johansen as chairman.

Both, as board members since 1985, have been on the majority side of several rulings in which Dotson dissented. The president's designation of the agency's chairman does not require Senate confirmation.

Before joining the board, Stephens was an aide to Sen. Orrin Hatch (R-Utah), the former chairman and ranking minority member on the Senate Labor and Human Resources Committee. Johansen is a career NLRB attorney.