Productivity improvement of a shipbuilding company depends on how efficiently its limited resources are managed and utilized. Recently, research on modeling and simulation (M&S) to support shipyard production management system has been being under study. The production management based on M&S rejects decision making on experience, and it can establish productivity improvement method based on quantitative and specific data. In this paper, M&S is applied to the long-term plan as a part of the production planning in shipyards. To this end, the long-term plan processes and related management systems are analyzed. Based on the analysis, a simulation model and an application system using commercial simulation software are suggested. And basic structure of the suggested system is based on web technology such as Rich Internet Application, web services protocol for compatibility with existing shipyard enterprise systems. Utilizing the results of this study, it is expected that shipyard production planners can settle down work flow, in which one can establishes the production plan, simulates the plan, and analyzes the results, enabling a more reliable production plans.