Focusing on the illumination coherence problem of the three-dimensional virtual scene, this study analyzed the environment mapping technology to improve the sense of reality. The light probe image was used to light the scene and the irradiance of the diffuse surface was approximated by using spherical harmonics function. By considering the shadowed diffuse transfer simultaneously, the soft shadow of diffuse objects was generated successfully under dynamic, low-frequency lighting environments. The experiment results showed that this algorithm approached accurately with high quality.