Abstract: Whether to calculate the impacting parameter accurately and efficiently which is about the kill element against the air target not only plays an important role in evaluating the kill probability of ammunition for aerial targets， but also plays an important indicator to assess the operational effectiveness of the missile weapon system. Based on the analysis of kill element and target motion model， methods of discreting cylindrical target into multiple small rectangles were proposed， and the angle calculation methods on the velocity direction of impacting and the axial section，cross section of the target，target angle and the target speed were deduced by using the judging criterion on hitting the target according to the relation between the distance of the intersection point to the four sides of the rectangle and the perimeter. And then the correctness and accuracy of the algorithm were verified by an example. The algorithm serves as basis for further studying the impacting parameter which is about the kill element against the aerial target.

Key words: kill element, aerial target, dynamic interception, kill probability, impacting parameter