According to the problem that duration can’t be c ontrolled effectively during the equipment development schedule, a method is proposed to confirm the critical path which applies Monte Carl o to the PERT network. Based on the classic PERT, this paper gives the definition of the activity cr iticality and critical path, studies how to use the Monte Carlo simulation to calculate the activity critical ity so as to confirm the critical path, and apply this method to analyze the PERT network of an independent air defense combat platform’s ca rrier subsystem successfully. The simulation results indicates that this method can effectivel y solve the problem that activity durations are random, besides, it offers an effective way to distinguish the critical technolo gy and analyze the influences to the development schedule.