Abstract: Aiming at problems of time-consuming and effort-consuming in terms of metro pantograph detection, an on-line dynamic measuring system based on image detection are proposed. Firstly, the system structure is introduced, including field data acquisition unit, field control unit, data analysis unit, data storage & publishing unit and client access unit. Then, the system scheme and working principle of pantograph head detection system, pantograph temperature measurement system, roof monitoring system and train number automatic identification system are introduced in detail. Finally, through computer simulation, the system is verified to be better than the manual measurement, featuring real-time, accurate and reliable advantages, therefore could meet the demands of Pantograph detection and maintenance.