According to the linear CCD measurement precision target projectile coordinate additional trigger screen transmits a trigger signal to decide when to start the acquisition problem. In the image acquisition process, the design of a trigger device and image acquisition device and receiving image data signal line array CCD camera, automatic detection and real-time transmission of the trigger signal of projectile. By studying the characteristics of projectile image and the hardware implementation method of the algorithm on the FPGA, the algorithm is verified by experiments using the currently collected images. Experiments show that the algorithm can effectively identify projectile signals and eliminate the interference of other non-projectile signals. This algorithm is very important to improve the triggering accuracy of linear array CCD precision target and to simplify the structure of linear array CCD precision target.