Based on the calculating method of internal impedance of cylindrical conductors， a chain network model of traction network is constructed by considering the transmission characteristics of multi-conductor lines in the traction network. The section division method of chain network and the simulating method of current source injected to lines on sections are also presented. Considering the large leakage conductance of rail to the ground， an equivalentπ circuit is adopted for simulating the chain network model to achieve satisfactory accuracy and reduce calculation burden effectively. Based on this model， the traction network harmonic current and voltage distribution in several power networks with different power supply modes are simulated. Simulation result is in line with measurement， which proves the accuracy of the model. Conclusions are derived from the simulation results.