President Reagan has announced three nominations to key labor-related posts.

Labor Undersecretary Ford B. Ford, 63, who served as acting secretary after Raymond J. Donovan resigned last year, was nominated as chairman of the Federal Mine Safety and Health Review Commission.

James M. Stephens, 39, labor counsel to the Senate Labor and Human Resources Committee and a top aide to Sen. Orrin G. Hatch (R-Utah), was nominated to the National Labor Relations Board. Stephens was associate minority counsel to the House Education and Labor Committee from 1977 to 1981.

If confirmed, Stephens would serve out the term of Republican Robert P. Hunter. Stephens' appointment would maintain the political balance of the five-member NLRB, with two Republicans, two Democrats and an independent.

Roger D. Semerad, 45, executive vice president of the Brookings Institution, was nominated to be assistant secretary of Labor for employment and training. He would be in charge of programs that spend $22 billion annually on job-training and unemployment services.

Ford's nomination would leave the undersecretary post vacant. Sources said it is likely to be filled by Dennis E. Whitfield, chief of staff to Secretary William E. Brock.

Semerad, who has held several Republican National Committee posts, as well as staff positions in the Nixon and Ford administrations, was a force behind a highly regarded jobs program called 70001 Ltd., which Brock frequently has cited as a successful model for training high school dropouts.