In order to make the operator freely walk in virtual environment (VE), a new prototype of VE system for assembly is presented in this paper. In this system, a special machine is designed and it enables the operator to walk inside the VE in any directions over a long distance without actually leaving the physical device. Images produced by the computer are projected upon the surface of a large spherical cap screen surrounding the operator by means of a group of high power projectors. Signals provided by the position sensors attached to the operator are used by the computer to update the projected images, which provides the operator the illusion of walking freely through the virtual scenes. This VE system can acquire wide field of view and form panorama surrounding the operator, which may enhance the realistic sense of simulation.