The beginning phases in simulation modeling are model building and validation. Because of the complexity of most simulation models, we need a mechanism to formalize models of reality, i.e., the object-oriented development. In this thesis, simulation modeling techniques and the process of the object-oriented development are described and integrated. With this background, a simulation design language has been developed and implemented using ISLDM/SEM which is a software life-cycle support system (LSS) generator, and is based on Entity Relationship Attribute (ERA) model. Using a set of tools in ISLDM/SEM, model completeness and consistency are checked and preliminary design lists are produced. This method is illustrated by an example. This thesis concludes that the object-oriented development is a good methodology for complex systems like simulation systems.