Aiming at the problem that the shooting difficulty of the new missile is increased because of its long range, fast speed and poor sea condition at the moment of target hitting, an algorithm for the miss distance of UAV is proposed. According to OpenCV function library and the principle of small hole imaging, the corresponding mathematical model is established. The calculation error is analyzed from 3 aspects: reference point selection, hull attitude and camera angle. The algorithm is validated by flight test and video recording on land. The experimental results show that the UAV cameras and miss distance calculation method meet the application requirements. Compared with the actual distance and Baidu map ranging distance, the measurement error is less than 1.5 m.