Abstract: As the core equipment in the traction power supply system, the fault early warning of traction transformers is of great significance to ensuring the stable and reliable operation of the traction power supply system. This paper elaborates on the overall design scheme of an on-line automatic monitoring and intelligent early warning system for traction transformers, conducts in-depth research on core monitoring technologies such as on-line monitoring of dissolved gases in oil, on-line partial discharge monitoring, grounding current monitoring of iron cores/clamps, bushing dielectric loss monitoring, vibration signal monitoring and winding temperature monitoring, optimizes the acquisition, transmission and synchronization mechanism of multi-source monitoring data, and constructs an efficient fault early warning and diagnosis model by combining multi-sensor information fusion technology. The system realizes real-time monitoring of the operation status, abnormal early warning and accurate identification of fault types of traction transformers, providing technical support for the safe and reliable operation and intelligent operation and maintenance of traction transformers.