The conceptual model's reuse is a problem in simulation system's development. In this paper, a conceptual model development method which supports reuse is given. The method centers about task, and generalizes the conceptual model development process to the following three steps: describing system structure and its implementation procedure, decomposing task and modeling behavior. After analyzing the method's reusability, its good impact for raising the model's reusability can be proved. Thereby, the method can be applied in the conceptual model's development of simulation system