With the fast development of electrified railway， the proportion of traction loads in the power system is increasing， which imposes effect on power system stability. However， the research on the synthesis load characteristics of traction power supply system is still weak. to solve the problem， a novel load model is introduced based on the actual load structure of the traction power supply system， which consists of an induction motor and a traction motor and constant impendence model. The model has simple structure， clear physical meaning and easy to use. The model is verified by simulation using Simulink. The results show that the model reflects a real traction system， and can be used in studying the effects of electrical railway on the power system.