Since the nature of the shipyard differs from general industry, a shipyard strategy formulation model has been developed based on its own business characteristics. This paper presents a proposed environment-based strategy formulation model for medium-sized shipyards. A questionnaire survey of the industry's stakeholders was carried out to identify the internal and external strategic factors of the shipyard's businesses. By using multivariate factor analysis, the strategic factors were identified in both new building and ship repair. The results were then used to develop business environment submodels and a shipyard business matrix. These industry based models were integrated into a shipyard strategy formulation model called YARDSTRAT. Its application and evaluation in two shipyards show that the proposed model could produce more comprehensive strategic options to sustainable competitive advantage for the companies.