A large thrust force permanent magnet linear synchronous motor that is used in a space electromagnetic launcher is designed. We study the thrust force and the normal force by taking some practical elements into account, including yoke thickness of primary and secondary cores, thickness and width of permanent magnet, air gap length, slot width, and turns of coils. We present an optimized design methodology for the maximum thrust force. The thermal analysis is verified by simulation and test. Also, the test result turns out to fall into correspondence with the theoretical analysis. It then would demonstrate the advantage of our method over some existing ones.