Abstract: The demand of tracking accuracy is very high in the boost-phase ballistic missile interception, how to fuse the data of many kinds of boost-phase detection equipments to get more precise data has become an urgent problem. To solve this problem, a new fusion tracking algorithm based on missile early warning satellites and radar was studied, a fusion tracking algorithm of boost-phase based on Bayes theory was proposed. The detection model and tracing model of missile early warning satellite and radar for boost-phase were established, the accuracy of this fusion algorithm was improved by the help of POFACETS' RCS simulation of one type of ballistic missile. Simulation results show that the result is more accurate than by using arithmetic mean on the limited sensors, this algorithm has high reliability.