An opticalcouplerisolated and automatically transmitted and received RS485 module is designed for system of environmentmonitor for warehouse. The isolation to TTL signal of opticalcoupler PC817 and transient voltage suppressor of TVS Diode are used to separate the system from outside signal. Then the CMOS inverter which consists of Schmidt trigger SN74LVC1G14 and RC circuit can largely reduce the delay during the signal conversion. Simulation of Multisim software and the results of actually application demonstrate that not only the TTL and 485 signal can be automatically converted to each other without any delay, but also the system can accurately receive the data from sensors. Aboveall, the module can greatly improve the reliability and realtime of data transmission in the system of environmentmonitor for warehouse.