An improvement is made to traditional particle system technology in rainfall simulation. In order to improve the authenticity and flexibility of rainfall simulation and speed up the rendering speed, the particle rotation, particle dynamic texture, dynamic color etc. are introduced. The structure of particles is simplified. Meanwhile, a funnel model is adopted to adapt to the characteristics of a flight simulator. Experiment results show that the proposed method has gotten realistic visual effect and real-time speed, and is especially suitable for large flight simulator scene.