Abstract: To avoid the faulty burst of anti-radiation missile (ARM) caused by proximity fuze early starting, a method was put forward, which could choose the starting position of the proximity fuze with the target sight line angular speed information from passive radar seeker, and could calculate the target sight line angular speed with angular information. The statistic relationship between target sight line speed and the missile-target distance was set up. According to the principles of start before the latest position and start as late as possible, the upper and lower limits of missile-target distance PDF were discussed respectively when the proximity fuze started. The simulation results show that: if ARM could not hit the target antenna directly, proximity fuze would start at the position with 30~120 m to the target plane; if ARM could hit the target antenna directly, proximity fuze would start at the position with less than 30 m to the target plane.