The temperature rise of the insulating material directly affects the safety and longevity of motor running. Based on a high一capacity air cooling salient pole synchronous motor，the calculation model of three一dimensional flow turbulent field and temperature field of rotor were built using the computational fluid dynamics(CFD)method. The interval cascade structure consisted of copper and insulation of rotor magnetic pole of salient pole mofor was simplified. The calculation method of equivalent thermal conductivity for simplifying interval cascade structure and the influence of the setting of periodic boundary between end fins on the calculation results of temperaturefield of the rotor of salient pole of synchronous motor were studied. Then，the results were compared with the experimental results which can verify the accuracy of numerical simulation. The results show that the calculation method ofequivalent thermal conductivity and the setting of periodic boundary between end fins can directly affect the accuracy of calculation results of temperature field.