To deal with the problems of complicated process, difficult operation and low efficiency for large-scale complex products assembly, a new immersive virtual environment (VE) with virtual reality (VR) technology is built in the process of assembly planning and training. The environment is composed of a free walk machine and spherical screen projection system. In this paper, a free walk machine with movement perception function is developed to achieve natural human-computer interaction. And an approach based on two viewpoints match is adopted to improve immersive effect of stereo projection in the projection system. On the basis of that, a geometry calibration method based on Bicubic NURBS(Non-Uniform Rational B-Spline) surface matching target-controlled dot-matrix is proposed to achieve non-distorted image on spherical screen. Finally, the environment is applied in the process of satellite assembly process planning, and the display result shows that the VE development is feasible and valuable.