Abstract: The substation system is divided into substation level, bay level and process level by IEC 61850 standard, and communication modes of process level and bay level are standardized. In order to improving the reliability of information transmission and reduce cost, based on the characteristic of data unilateral transmission mode between bay level and process level and the Ethernet physical layer chip DP83849IF, we design a kind of single input multiple output data transmission device to replace the switch used to send data from single process level device to multiple bay level devices. Test results show that the bit error rate and transmission delay index meet the need of current substation development.