Abstract: Multi-stage pneumatic telescopic cylinder is more and more widely used. This kind of pneumatic cylinder has many specifications, complex structure, many assembly links and high precision requirements. However, the current conventional manual sub-process assembly method is difficult to meet the assembly requirements of products. Taking a multi-stage pneumatic cylinder as an example, this paper analyzes the assembly process requirements, finds out the problems existing in the assembly process, improves the assembly process with very low input cost by using the existing equipment, and solves the assembly problem of a pneumatic telescopic cylinder.