Abstract: In this paper, we propose a new particle-based fluid-fluid collision model for immiscible fluid animation. Our model consists of two components, namely, collision detection and collision response. A useful modeling feature is that our model not only can prevent immiscible fluids from mixing with each other, but also can allow one fluid to run through or to wrap around another fluid. The model is very flexible and can work with many existing particle-based fluid models. The animation results are presented and show that the proposed model can produce a variety of fluid animations.