Abstract: For high-voltage cables installed in urban underground utility tunnels, the accuracy of fault location for partial discharges is of significant importance for their operation, maintenance, and repair tasks. This paper designs and develops an online partial discharge monitoring system for high-voltage cables, elaborating in detail on the scheme design of the partial discharge acquisition device. By adopting synchronization Ethernet timing technology based on IEEE 1588 and high-frequency sampling technology, the system effectively enhances the localization accuracy of partial discharge signals, thereby addressing issues associated with traditional fault location methods, such as low precision, poor stability, insufficient anti-interference capability, and operational complexity.