Abstract: Position deviation measurement between projectile explosion and target is important for accuracy test of naval gun system. By recording the arrival time and output amplitude of acoustic-optic signal during firecracker explosion, the concept of detecting the explosion signal of small equivalent gun powder based on acoustic-optic method was verified. The arrival time difference of acoustic wave and light wave was 14-7 ms at an explosion distance of 5 m. The receiving distance of the sensor was 8 m~20 m at different angles. The arrival time of the explosion acoustic-optic signal and the receiving distance of the sensor were tested. The results validated the feasibility of making the measurement using acoustic-optic signal. Combined with the distance error data between projectile and target, the statistical analysis of the deviation data could be done.