In order to solve the problem of serious highway overloading, a novel piezoelectric WIM (Weigh in Motion) sensor is put forward, in which PVDF (Polyvinylidene fluoride) film served as a sensitive component. In this paper, the working mechanism of the piezoelectric WIM sensor is introduced and the Finite Element Analysis software ANSYS is used to analyze the electromechanical coupling characteristics of the sensor. Simulation results show the relationship of the magnitude of electric charge induced from the sensor with a monolithic PVDF layer, or series／parallel connection of bi-layers. A simple processing circuit is designed to covert PVDF high output impedance to low output impedance and the collected electric charge inside the sensor can be simplified efficiently. Finally, in-door simulation and out-door dynamic experiments using a domestic car are carried out to certificate piezoelectric WIM sensor, the results show that the sensor prototype has a relatively obvious response rate and give an on-line testing and data analysis of monitored vehicle status.