In this paper, the functions of the received power-distance were deduced and analyzed under the different train operating conditions at first. Based on these functions, an improved path loss model, the triple-slope path loss model, for high-speed railway control signal was raised. And the proposed path loss model was verified by the test data at high speed railways in China. The application area of the proposed model, the error analysis between the proposed model and the experiment data was outlined in this paper too.