Abstract: With the gradual improvement of reliability and quality requirements for the development of electric power in China, and the rising rate of cable usage in power lines, the 10 kV Ring Main Unit(RMU) has become an essential component for ensuring safe and reliable operation and for managing switching operations. Consequently, monitoring and diagnostic technologies for the operational status of RMUs have become increasingly important. This study developed a detection and diagnosis device for assessing the mechanical characteristics of 10 kV RMUs to meet these technological requirements. The device utilizes high-precision sensors to capture physical parameters such as the current of closing and tripping coils, and applies fault diagnosis algorithms to identify mechanical characteristics. By analyzing these characteristics, the device can evaluate the mechanical performance of the RMU switches, diagnose potential faults, and issue warning alerts, thereby enhancing the reliability and safety of the equipment. Test results indicate that the device offers accurate detection, providing precise and intuitive data support for refined operation and maintenance of RMUs.