According to the IEC600448 standard definition of merging unit, starting from the function of the merging unit, using the software of MATLAB to receive simulation of multi fault information of field power system, and sending the merging unit with FT3 frame format through the Ethernet, processing the received data with the merging unit with FPGA as hardware core, finally the data is sent to the two side of the device to receive the data realtime display through the Ethernet. The study based on the experimental platform, mainly described the structure and function of each module, including the MATLAB transmission module, FPGA receiving and optical fiber sending module and Manchester coding and decoding and data display module. The hardware platform is built and the test result of the software is given.