With the effect of waves on ship in the seaway, the ship sways ceaselessly. These sway conditions affect the ship equipments and assignments directly. It is very important for us to set a system and to use the system to simulate ship navigation in ocean conditions. In the article, the authors have established the ship simulated motion framework based on HLA. In this framework, several federations which are taken as the basis to simulate ship motion and the seaway environment have been set up. The framework provides an environment and platform to study the assignments on board. The ship simulated motion system is developed with VC.Net and Vega prime technology. This system can simulate the motion of ships in deferent sea conditions. At the same time, it also can provide a basic research environment for the further study of the diversity of assignment process on board.