With the continuous development of the virtual reality technology, the requirement for the authenticity of the virtual scene is getting greater and greater. However, there are a lot of data to be rendered in the virtual scene, which is caused by the complex terrain as well as a large number of vegetation and buildings. As a result, the rendering speed becomes a bottleneck of the virtual reality technology. In the existing research, it is impossible to improve the rendering speed of the illusion engine very well. Some problems can also appear about "breakthrough" and the poor effect of removing the invisible model. In this paper, a kind of parallel and double-layer cut algorithm for game threads and rendering threads is presented. Firstly, game threads and rendering threads are paralleled in the illusion engine to improve the rendering speed. Then, the fade in-and-out levels of detail algorithm are applied to cut the first level. Finally, the fade culling algorithm is adopted to cut the second level to improve the culling effect. The experiment shows that the rendering speed of the above method is improved by forty percent compared with the rendering speed of serial threads. Its frame rate is also improved by fifty-five percent compared with the traditional single-layer cut algorithm.