Through numerical simulation, missile cold ejection process dynamics and technology feasibility were studied. Based on the theory which relies on air supply from ground air source to push missile departing from the launcher, depending on virtual prototype technology and FEA method, then one air defense missile's ejection process rigid-flexible coupling dynamic simulation model was built in Adams/View. Wind velocity and clearance between slider and guide were defined variables before simulation. The dynamic data of launcher's vibration, missile's disturbance and the influence of different clearance and wind velocity on missile muzzle attitude were obtained. It shows that wind velocity has a greater impact on missile cold ejection, reasonable clearance is conducive to missile cold ejection from launching canister.