In precision test of laser irradiation，the position and size of laser spot on the test target will change with the aircraft route.To properly set the target，parameter estimation method is proposed.The estimation model of test target parameters is built，and calculation requirement of test target parameters for different aircraft routes is met，which provides a feasible way for the target settings.Test results indicate that laser spot can be measured totally by setting the proper parameters，such as oblique angle，size and cross centre of the target board，which provide a reference for measuring laser radiation sensitivity accurately.