Abstract: In order to realize the integration of simulation of the train power supply system of alternating current (AC) electrified railway, and considering the mutual influence of multiple loads at the point of common coupling, the train power supply system was divided into source layer, grid layer and load layer. By establishing the chain circuit model of transmission line, feeder and traction network, and the conversion relationship model between the interfaces, a general model of the source-grid-load unified chain circuit of the train power supply system was constructed. Based on this model, the dynamic power flow calculation of the train power supply system was carried out, and the basic models that use current source and power source iterative models were established respectively. In order to reduce the time-consuming of computer simulation, on the basis of the basic model, a correspondingly improved model and solution method were proposed. Taking an electrified railway line as an example, the calculation accuracy of different solution methods, iteration convergence times, consumption of computer simulation time and model application scenarios were simulated and analyzed. The results show that the accuracy of the basic model is the same as that of the improved model, but the time consumption of the improved model is less; it is necessary to calculate the load flow of the source network, especially in the weak areas of the power grid; , and the application scenarios of the power source iterative model are wider than that of the current source iterative model.