The interactive system is one of the most important parts in the integrated environment of modeling and simulation. It mainly resolves the relationship between the human and the computer of simulation (CS), and it makes it convenient for the users to communicate with the CS at high speed. It can supervise the running of simulation in real-time. We briefly introduce the system environment at first; several aspects, for instance, designing the system as a whole, analyzing and processing the interactive commands, realizing the functions, are discussed in this paper. Moreover, we introduce something about the user interface.