In recent years, cost reduction is strongly required for most system development. In plant systems engineering, integration of information which is commonly utilized in some design phases from the plant design level to the programming level should be considered. In this paper, we propose a reusable object model for plant systems engineering, realizing the integration of information through design phases. We will propose a machine template as a unit of reusable objects. We also have developed an engineering environment tool based on the reusable object model and applied it to building several systems. As a result, the system development time could be decreased to 2/3, as compared with the past system of the same scale.