Modeling and collision detection algorithm is the premise of the real-time in virtual surgery. Here, we extract the CT point cloud data from patients. Then, we model for soft tissues and organs based on the algorithm of octree subdivision and hierarchical structure of bounding sphere. In order to improve the real-time of the collision detection, the physical models of the surgical instruments are simplified to balls or lines. The geometry remains unchanged, and it thus does not affect the operation of the virtual visual while the speed of the collision detection is improved greatly. The experimental results show that the algorithm can accurately detect the point of virtual contact with the virtual mode l of surgical instruments, and collision detection in real-time have increased considerably. Simplified average collision detection time is 10% of the original.