Abstract: SAR imaging simulator is an important tool for understanding and implementing the SAR images. In the light of the structural features of buildings, a novel fast SAR imaging simulator for urban structures based on facet projection model is proposed to meet the requirements of the SAR image interpretation applications for buildings. The geometry mapping process from the target model to the image-domain is accelerated by using simplified ray tracing algorithm, and the facet projection model is performed to reduce interpolating error from scattering facets to resolution cells. Compared with the traditional SAR image simulator, this simulator strikes a balance between accuracy and efficiency. Some experiments validate the facet projection model and demonstrate the efficiency of the simulator, which will offer a higher value of practical applications.