S7 communication can be used for Industrial Ethernet, PROFIBUS or MPI network. In this paper, Achieved by PLCSIM between two S7-400PLC based on TCP / IP, S7 communication, Describes the configuration of an S7 communication and programming. For two or more communications between the PLC simulation, PLCSIM the same. PLCSIM also supports MPIbased S7-400 S7 communication and S7-400 DP-based simulation of the S7 communication. The S7 communication network configuration and programming is basically the same, and it can provide some reference value for the analogous project.