The design of hydraulic shift actuator is emphasis and difficulty of automatic mechanical transmission (AMT), and the performance of hydraulic shift actuator directly affects the ride performance, comfort and safety of automobiles. Based on a five-speed manual transmission, a hydraulic shift actuator was designed. The hydraulic system of the shift actuator was designed, the main hydraulic components were selected according to the design calculation, and the work process of the shift actuator was described in detail.The shift actuator was practically manufactured, and the 5-speed manual gearbox (MT) was transformed into AMT. The result shows that this hydraulic shift actuator can complete choosing and changing gear gently of the five speed gearbox, and this structure is simple, accurate positioning, sensitive respond, and its shift quality is safe and reliable. This shift actuator will be worth application and dissemination.