An embodiment of the invention discloses a system direct-current voltage monitoring device and aims to solve the technical problem that a power module and integrated circuits are placed on one circuit board along with system miniaturization and integration, the proximity principle is used to reduce unnecessary interference, a system board and card power supply becomes the key part for stable system performance, measuring tools such as an oscilloscope and a multimeter are used to measure direct-current voltage and direct currents during the debugging of the board and card power supply in a system, but the voltage and the currents are difficult to monitor when boards and cards are mounted in a cabinet.