The safety assessment of the structure related to people has become the most important part in the process of the design. Especially, in the case of a ship, as regulations about the safety of passengers and the pollution in the ocean are strictly reinforcing, the safety assessment has become the most important part in the process of the design. In this paper, we suggested network-based simulation system framework using HLA (High Level Architecture) among many kind of simulations to assess the safety of the ship. In addition, the visualization method which is composed of graphic user interface for ship modeling and the visualization of ship motion is presented.