Abstract: Recently most researches on ad hoc network were conducted by simulation. As to the simulation of MAC protocol, the large simulation softwares are usually difficult to use and inaccurate. A small-size ad hoc MAC protocol simulator is therefore designed to study relevant network protocol, which simulates physical channel with data byte as minimum processing unit that is suitable for studying MAC protocol. With the network activities visualized, it is convenient for early development and debugging of MAC protocol. This simulator is designed with an object-oriented method and multi-thread protocol model to provide well its extensibility and introduce a class of RXMitter to solve the synchronization problem. In addition, a new traffic model is proposed which is more suitable for MAC protocol simulation. An implementation method and related tests are given to the simulator.