President Reagan yesterday announced his seven nominees to the new U.S. Sentencing Commission, which will write guidelines designed to reduce the disparity in prison sentences of persons convicted of federal crimes.

Under the Comprehensive Crime Control Act of 1984, which created the commission, the panel must include three federal judges. Reagan nominated U.S. District Court Judge William W. Wilkins Jr. of South Carolina, a former aide to Sen. Strom Thurmond (R-S.C.), and one of Reagan's youngest nominees to the federal bench. If confirmed, Wilkins would be designated chairman. Also nominated were U.S. Circuit Court Judge Stephen G. Breyer of Massachusetts, a former chief counsel of the Senate Judiciary Committee and one-time aide to Sen. Edward M. Kennedy (D-Mass.), and George E. MacKinnon, a senior judge for the U.S. Court of Appeals for the District of Columbia, on which he has served since 1969.

The president also nominated Ilene H. Nagel, a law professor at Indiana University; Paul H. Robinson, a law professor at Rutgers University; Helen G. Corrothers, a member of the U.S. Parole Commission since 1984, and Michael K. Block, a professor of management and economics at the University of Arizona School of Business and Public Administration.

The panel is supposed to submit guidelines to Congress for approval next year.