The crossbow first appeared in the Spring and Autumn Period and is said to have been invented by Qin Chu. In ancient times, it was called nest bow, and now it is also called crossbow (from English). It is a kind of bow with arms, which is mainly composed of crossbow arm (crossbow body), crossbow (crossbow wing), bowstring and crossbow machine. Because there is no need to aim at the same time when pulling the string, the requirements for users are relatively low, and the loading time is much longer than that of the bow, but in general, it has a longer range, stronger lethality and higher hit rate than the bow. In ancient times, it was a powerful long-range killing weapon. The range of the strong crossbow can reach 600 meters, and the range of the bed crossbow is more than 1000 meters. According to different threading methods, it can be divided into arm stretching, leg stretching (foot stepping) and waist stretching. Europeans use various threading devices to wind strings.