Abstract: Tomosynthesis can reconstruct any sectional image of object using limited angle projection. Before the research of reconstruction method,projection simulation is an important step,this paper proposed a projection simulation method based on GPU Raycasting algorithm. Comparing to CPU simulation method,GPU simulation method is faster in calculation and much closer to the practical projection based on hardware-based trilinear interpolation. This paper simulates projection using traditional CPU method and GPU method respectively,reconstructs the projections above by ART algorithm and Wavelet-Galerkin algorithm and achieves good results.