Aiming at the problem of the traditional ejection device of aircraft missile,a hydraulic catapult mechanism was designed in which accumulator supplied ejection flow and servo valve was taken as core control element.The operating principle of the hydraulic catapult mechanism was described,the component parameters were calculated and the simulation model was created based on AMESim.The simulation results show that the hydraulic catapult mechanism can make the missile speed up to 8 m/s in 60 ms time;the buffer efficiency is up to 98% within the 20 ms