Abstract: Hybrid excitation synchronous machines（HESMs） have the advantages of controllable magnetic field, high efficiency and good control ability, so they will have good prospects in electric vehicles and wind power generation system. The temperature rise of HESMs directly affects the performance and reliability of the machines. Based on the structure and cooling condition of the HESM with modular stator, the lumped parameter thermal model of the machine was established. The equivalent thermal conductivities of the modular stator armature windings and the excitation windings were determined. The accuracy of the lumped parameter thermal model was verified by the thermal test of the 100 kW prototype. The influence of armature winding current densities on the temperature rises of similar cooling conditions and power levels HESMs was analyzed. At the same time, the influence of excitation winding current densities on the temperature rises of HESMs was analyzed. The research work provides an effective calculation method for the thermal calculation of the HESMs. At the same time, the research work provides a reference for the design of similar cooling conditions and power levels HESMs. Therefore, it has important theoretical significance and engineering practical value.