The composition and reuse of simulation model is currently a hot research topic in the area of complex system modeling and simulation. A unified simulation model representation is one of the key techniques to facilitate reuse. The model representation concept and its role in simulation are present firstly. The reusable simulation models, when compared to common simulation models, give some special requirements to the specification and method of model representation, which are summarized in the second part. Three traditional simulation model representation methods, i.e. representation by programming language, by simulation language and by generic model language, and their respective shortcomings when representing reusable simulation models are analyzed next. The advantages of metamodel in software representation are widely acknowledged in recent years. With this in mind this paper presents a metamodel based method to represent reusable simulation model, and the design considerations of...