A water tank sentry system with a single pole device, including a ground bolt, observation pier, main rod, solar panel, IoT edge gateway and monitoring component; the ground bolt is buried underground, the observation pier is fixed on the top of the ground bolt, and the main rod is vertically set and fixed on the top of the observation pier; solar panels, IoT edge gateways and monitoring components are all installed on the main rods; the present utility model adopts an integrated method to realize the intelligent monitoring of the reservoirs and dams, realizing that various sensors and intelligent devices can be powered by solar cells, depending on IoT edge gateways to realize the data collection and calculation of various sensors and communication with the server to report the data, so that the state monitoring of the reservoirs and dams can be safely and reliably carried out with small floor space and simple and easy deployment, and 220V city power supply is not required, which saves labor.