Abstract: In this paper, the hardware design of the MUX is introduced, which centralizes 3 synchronous/5 asynchronous or 8 asynchronous data on a single channel. With the internal master serial port and external master serial port connecting to communication equipment, the data multiplex is implemented, which is able to keep working by swithing automaticly to reserve line when the current line fails to work normally. It also makes the communication more secure by encrypting the data issued at the port and the communication line. This paper also studies the interrupt system, data communication control, system reliability design.