The realization method of communication simulation system for the IEC 61850-based online monitoring devices is presented for the interoperability and avalanche tests of online monitoring systems for electrical equipment. This system simulates various types of data communications between online monitoring devices in the bay level through loads of SCL information model description files for the online monitoring devices, hence the analog simulation tests for the systems in the station level are realized. It is proved that the communication simulation system for online monitoring devices may not only shorten the test cycles but also reduce test difficulties during quality tests and project debugging.