To enhance measure precision in across screens measure system, the methods to acquire the time including projectile nose, projectile bottom, middle screen, and generalized correlation are put forward and further researched. The screen information moment acquiring was analyzed base on across screen measure system. According to the characteristic when projectile enter screen different location and the relation between projectile length and screen thickness, the output analog waveform features in detection circuit were discussed and analyzed. Base on the output analog signal waveform, the trigger moment in sky-screen was ensured, which may be use the projectile nose and bottom. To solve the influence of incline screen to measure precision, the output signal was gather by computer and apply the technology of generalized correlation to calculate the time value between screens. Through the experimentation and analyze, three methods both can improve measure precision in across screen system, especially, the method of correlation is more stably.