This paper studies an auxiliary poles technique that is used to reduce the end effect detent force for permanent magnet linear synchronous motor (PMLSM). Based on the lateral force method, the analytical model of the end effect detent force is built. The expressions of the optimal position and the optimal width for the auxiliary poles are derived. Through the use of finite-element calculations, the influence of the position, width, and height of the auxiliary poles on the end effect detent force is obtained. In addition, the detent force characteristics for five PMLSMs with typical slot–pole combinations after adopting the auxiliary poles are analyzed. The inhibitory effect of the auxiliary poles on the end effect detent force is separated from the slot effect detent force using harmonic analysis. The simulation results of the optimal auxiliary poles positions match the analytical expressions well, which proves the correctness of the analytical model. Finally, a prototype of the PMLSM with auxiliary poles, which has a better structure strength and eliminates the installation error, is manufactured and tested.