This paper makes researches on multiple independently reentry vehicle (MIRV) ballistic mis- sile interception. It breaks through traditional intercepting methods of missiles and combines comba- ting time characteristics of MIRV missiles with the principle of computer process schedule. In this paper, a way of firstly intercepting the target missile with higher threaten grade is proposed. This method determines the threaten grade of the attacking target according to computer process schedu- ling algorithms, then appljed a proportional navigation guidance law to intercept target missiles in priority so that it achieves the effect of less damage. The simulation results indicate that it is effec- tive to use the proportional navigation guidance law based on the process scheduling to intercept tar- get missile. It possesses referential value in modern weapon combats.