Computer simulation based methods have enjoyed widespread use in healthcare system investigation and improvement in recent years. Healthcare systems are based on human interactions and Emergency Departments (ED) are one of the key components of the healthcare system. The efficiency and quality of service in ED have a great influence on the whole healthcare system. The first step to intensively study the emergency department, to find its underlying problem or to provide the best service with limited budget, should be to create a realistic computational model of the ED. Agent-Based Modeling and Simulation (ABMS) is an excellent tool to deal with complex system like ED. This paper presents a generalized agent-based model of the emergency departments. It was designed based on the survey of different EDs and with the participation of sanitary staff in ED. The model ss a generalized ABMS-based computational model of ED without dedicating to a specific ED, thus it can be used to simulate different EDs through after a proper tuning process. The model has been implemented and verified in a Netlogo modeling environment and can be used to simulate different EDs through a tuning process.