Abstract: Hybrid excitation synchronous motor（HESM）, with the superiority of field adjustable and wide speed operation range, has broad application prospects in industrial and military. This paper proposes a novel copper loss minimization flux weakening control method for HESM based on vector control and speed region control. The proposed method adaptively adjusts the coefficient of flux-weakening base speed using minimum copper loss as optimization target, so that q axis, d axis currents and exciting current are optimally allocated under the condition of armature terminal voltage limited. On the basis of analyzing the influences of the coefficient of flux-weakening base speed on the operation performance, an adaptive control method is adopted to adjust it for improving the comprehensive performance of HESM, including speed operation range, efficiency and dynamic behavior. The correctness and effectiveness of the proposed method are verified by simulation and experimental results, which shows that the comprehensive operational performance of HESM can be optimized by the proposed flux weakening control method.