As for the issue of shipboard missile launch, the research on the influence factor of the missile muzzle attitude was conducted. The numerical simulation was done for random motion of ship based on the energy spectrum of principle; The multi-body dynamics model of the launch system was built and the influence of rolling, pitching, heaving, navigational speed and clearance on missile muzzle attitude was analyzed; The parametric model was built and the clearance was optimized. The analysis results show that rolling, pitching and gap would influence the muzzle attitude of the missile, but the heaving and the gaps do not. The conclusion is that the design project for the system is feasible, which makes estimate for the current design and supplies the reference for further design of the launch system.