As the chaff centroid jamming can introduce the guiding error of the anti-warship missile's seeker and decrease its hitting probability, a new quantitative analysis method and a mathematic model are proposed in this paper to evaluate the success jamming probability. By using this method, the optimal decision scheme of chaff centroid jamming in different threat situations can be found, and also the success probability of this scheme can be calculated quantitatively. Thus, the operation rules of the centroid jamming and the tactical approach for increasing the success probability can be determined.