Precision and efficiency are the two most important goals of simulation. As far as communication networks are concerned, for the great complexity of their topologies, protocols and traffic, how to simulate them efficiently has been a hot spot in the recent research. This article first emphasizes the importance of the survey before the simulation begins, because it can make the target of simulation clear. Also, during the modeling phase prior to simulation, we should consider adequately the characteristics of the communication network to be simulated and adopt some methods in order to improve the simulation efficiency.