The invention relates to an environmental monitoring device for a power communication system, and in particular relates to a monitoring system for ensuring optical cables in a cable trench and a vertical shaft to work safely and reliably. The environmental monitoring system based on Lora spread-spectrum wireless long-distance comprises a field data acquisition part, an intermediate data server part and an upper-end application display part; the field data acquisition part is composed of three sub-systems comprising a water-level monitoring sub-system, a temperature detection sub-system and a gas detection sub-system, mainly acquires temperature, water-level and gas information in the cable trench and the vertical shaft, and sends the temperature, water-level and gas information to the nearest Lora/4G gateway equipment after sorting out the temperature, water-level and gas information; the Lora/4G gateway equipment forwards the received information to the remote intermediate data serverpart; the cloud server of the intermediate data server part comprises data storage, data management and data analysis and early-warning modules; and the intermediate data server part and the upper-end application display part are in communication connection. The problem that the traditional wired communication mode is not reliable any longer when the environment of the cable trench is changed canbe solved.