Based on the analysis of the cooperative engagement of SAM troops and air arm, the selection and optimization method of air -ground cooperative engagement is put forward. Firstly, the overall combat efficiency under different cooperative engagements is calculated and the best pattern is selected. Secondly, the adjusting plan is given according to the strength ratio between enemy and ourselves, and simultaneously the relevant mathematic models are given. This method is proved to be effective by a certain example. The method can provide reference for the decision - making of air - ground cooperative engagement.