Hit accuracy is one of the key metrics for evaluating weapon systems. This paper presents a calculation method of hit probability for homing guidance weapon system, and also introduces the principle and method of accuracy analysis of weapon system, the relation and influence of main error sources. The hit probability is decomposed into three parts: target identification probability, midcourse and terminal guidance shift handover probability, and terminal guidance hit probability. Based on the Bayesian theory and the prior error source distribution, the accuracy of the weapon system is analyzed by mathematical analysis, Monte Carlo targeting and simulation analysis. The simulation example shows that the method can calculate the hit accuracy of homing guided weapon system effectively.