“Sword's Trail” means the “lighting effects” when weapons like swords are waving in 3D games. This article analyzes the rules of the image’s changes for “Sword’s Trail’ effect, and hands out an practical algorithm of the effect mentioned above. With this algorithm, the application can automatically produce the “Sword’s Trail” effect of weapons. In combination with real application experience, this article also proposes an ameliorative method of the algorithm. The algorithm can combine with a variety of game engine, and has been applied successfully in a lot of 3D games.