Abstract: Micro-Doppler is a unique characteristic of micro-motion targets, as an important signature of truck, micro-Doppler generated by rotation of wheels will offer proof for recognition of the truck. Firstly, on the basis of scatterer model, taking the relative position between radar and truck into consideration, the occlusion model of truck is established by applying the Painters algorithm in computer graphics; then the micro-motion of truck is modeling, the variation of Doppler and micro-Doppler with azimuth, depression angle, velocity and acceleration is analyzed for non-rotating scatterers and rotating scatterers respectively, which is the fundament of signature extraction and target recognition for the truck based on micro-Doppler. The effectiveness of the method and correctness of the analysis are proved by simulation results.