The path loss of wireless channel is the biggest factor affecting transmission efficiency of the electronic toll collection（ ETC） system. Considering that the complex surrounding environment will cause electromagnetic wave propagation loss in the channel under the condition of multi-lane

a channel propagation loss model of ETC system by analyzing the geometric characteristics of multipath radiation is proposed. The influence of the path loss caused by the bypass large vehicle and the front ground or the engine hood is discussed. The diffraction path caused by the bypass vehicle and the reflection path caused by the front ground or the hood are the main factors influencing the system channel propagation factor. The simulation results of the specific scenario can be drawn as follows: when the distance between bypass vehicle and road side unit（ RSU） is 0. 6 m and the distance between identified vehicle and road side unit（ RSU） is smaller

the system path loss is smaller.