Line start permanent magnet motor (LSPM) is kind of a typical model of the high-efficiency motor at the constant velocity. In this paper, we will deal with the cost reduction design of a three-phase line start permanent magnet motor (LSPM) due to high cost of the permanent magnet (PM). Cost reduction can be effectively achieved by reducing PM volume through optimal method. Therefore, Original LSPM motor' experiment data and FEM results of the LSPM motor performances such as linkage flux, back electromotive force (EMF), magnetic force, etc. were analyzed according to slot form of PM. We can finally select the proper slot form of PM which improves the performance and reduces manufacturing cost of the LSPM motor.