Abstract: The mechanism of virtual reality simulation is deeply discussed. By means of the popular VRML 3D constructing language to build virtual reality scene and objects, and Java general programming language to code the mobile engine, which not only can complete the normal numeric simulation but also drive the virtual reality objects running according to the simulation event logic, this simulation system is realized on normal computer without any extra hardware requirements and meets the fundamental interactive requirements of virtual reality system.This fundamental, practical but powerful virtual reality simulation system is mainly applied on world wide web, and can be easily installed in any Java integrated development environment and extended to more utilized fields. Furthermore, a virtual reality simulation model for the assembling process of Boeing 737-700 aircraft is researched and constructed by such theory and methods. Finally, the future development of this virtual reality simulation mechanism is also discussed to show the prospect.