According to the timeliness and accuracy of collision detection in missile flight visual simulation, this article puts forward an optimization algorithm for collision detection based on mixed bounding box. This algorithm established bounding box tree beginning with the hierarchical structure. In this bounding box tree, Sphere is used in upper level, and OBB is chosen in the lower level. At the same time, the intermediate buffer layer is removed. Then after the realization of this algorithm in missile flight visual simulation system, its performance is analyzed and especially compared with intersect vector collision detection algorithm and OBB bounding box collision detection algorithm. The analysis and comparison show that, this mixed bounding box algorithm can effectively improve the accuracy and timeliness of collision detection in missile flight visual simulation.