Abstract: With the drastic increase of the use of electronic power converters and electric motor drivers in modern aircraft power supply systems, their negative impedance characteristics are found to seriously affect system stability. This article analyzes the stability of a synchronous generator-rectifier system with constant power loads (CPLs) by the state-space averaging method. Small signal models of the synchronous generator-rectifier systems with concurrent resistance and constant power loads are established. Considering the effect of the load parameters upon system stability, the limit value and stable operating areas of the system with constant power loads are obtained. The phase margin of the system is increased by 53°, and the stability is obviously enhanced by the designed series correction, meanwhile, the response speed of the system is to some extent improved.