Traction power supply system is an electrical power network used to receive power from three phase power transmission system and supply power for the train driving on the single-phase AC power system electric railway, mainly composed of the traction substation, traction network, partition substation, switch substation and other components. Based on analysis of the compositions of high-speed railway traction power supply system and the autotransformer power supply mode in parallel entirely, this paper establish a simulation model of traction power supply system in the MATLAB/Simulink environment, and a variety of fault conditions in the traction power supply system are simulated, therefore, provided a reference for research on the protection scheme and fault impedance location scheme.