Computer simulation of special effect is an important part of the visual surgery simulation system. Rapid and accurate simulation of special effect can make the visual surgery more realistic. Simulation of bleeding is essential to surgery simulation system. This paper focuses on small amount bleeding appearing in a small injury. It forms a bended bloodstream on the organ surface. A simple model is established. The bloodstream is rendered by the metaballs method. During the simulation, only the dynamic simulation of the leading end of the bloodstream is considered while the rest of the bloodstream is rendered statically. This combination of dynamic simulation and static rendering can reduce the expense of computation and make the model more real and more computationally efficient for real time animation.