Abstract: Objective: To ensure safe operation of contact rail power supply system during service and guide operation, maintenance and repair, a new type of metro vehiclemounted power supply contact rail geometric parameter detection device is proposed.Method: Its definition, composition, detection principle, software functionality are expounded, and the accuracy and practical application onsite situation of the detection device are verified. Through longterm tracking experiments and an enormous amount of data analysis, the actual application accuracy of the power supply contact rail detection device is verified. Specifically, a detection vehicle is used to collect contact rail geometric parameter data by detecting twice on roundtrip at a speed of 30 km/h, and the analysis program is used to export detection data four times while extracting the working height and offset value at the positioning column. At the same time, the accuracy of the data including contact rail working height and offset value is compared dynamically and statically with manual measurements, and the repeatability error of the detection system itself is compared. Result & Conclusion: In the dynamic and static comparison of the measured values at 50 positioning points, dynamic and static errors of working height measurements of 48 are within ± 2 mm, accounting for 96%; the dynamic and static errors of only two measured values are beyond ± 3 mm ( accounting for 4%), meeting the accuracy requirements; the dynamic and static errors of 50 offset values are within ± 2 mm, accounting for 100%, meeting the accuracy requirements; comparing the fourtime four measured values of the 50 positioning points, the repeatability error of the working height is within ± 2 mm, accounting for 96%, meeting the accuracy requirements; the repeatability error of the offset value is within ± 2 mm, accounting for 99%, meeting the accuracy requirements. The new metro vehiclemounted power supply contact rail geometric parameter detection device has been in normal service on six main line contact rail main lines for nearly 1.5 years, completing approximately 130 dynamic contact rail dynamic detection tasks, with a total detection mileage of over 10,000 kilometers. Under longterm tracking, the equipment and device are stable, and the accuracy meets the onsite usage requirements.