The isolated 4-port RS485 hub realizes 4-channel RS485 slave ports through 1-way RS485 / RS232 expansion. It can automatically sense and control the sending and receiving direction of the data flow, deal with the problem of RS485 transceiver conversion delay, and apply to the distance extension (relay) and data expansion of RS485 communication equipment in complex and harsh industrial field, and effectively solve the problem of RS485 star structure.