Abstract: The DC power supply failure of the isolation switch in substation occurs frequently, which has security risks to the power grid. In order to monitor the operation parameters and status of the DC power supply of the isolation switch, this paper designs a set of intelligent online monitoring system for DC power supply, collects the relevant parameters of the DC power supply through the data acquisition terminal, and sends them to the central processor for data analysis and processing. At the same time, the running information is sent to the monitoring background for data saving and display. The system can monitor the real-time operation data of the power system and give early warning to the over-limit data. It can also test the DC power supply through the simulated load function, and the monitoring background can fully monitor and manage. Improve the reliability and stability of plant and station operations, reduce failures and downtime, and improve production efficiency and grid security.