During water-exit of underwater vehicle, the high pressure， which the local cavity collapse of underwater vehicle causes, poses a great challenge to the vehicle structure. The cavity collapse during vertical water exit of an underwater vehicle is simulated by a viscous flow solver with homogeneous multiphase flow model. The shrinkage and collapse of cavity zone and violent changes of the pressure field have been captured during the simulation. The changes of cavity shape and pressure field at different water exit velocity have been analyzed. It has been concluded that higher velocity may cause the delay of cavity total collapse and the max pressure point to transfer backwards.