In order to enhance the immersive realism of motion blur in virtual reality system, an improved post-processing algorithm of motion blur based on Graphics Processing Unit (GPU) is proposed. Depth value of full resolution texture maps in before and after frames of scene rendering are stored in the depth buffer in this algorithm. It uses its depth information and mapping matrix of the current frame to extract the world coordinate of the object, and gets the velocity vector. Then along speed vector it samples Gaussian filters. Fuzzy factor is introduced and fused weighted linear sample values to achieve the most realistic motion blur effect. The results show that: the proposed algorithm withgood real-time and realism effect will not only not affect the fluency of rendering large virtual reality system, but also solve over ghosting or streaking.