Abstract: Analysis and handling of 500kV GIS system current abnormality in an Ultra-High Voltage substation. In response to abnormal current conditions in the 500kV system of a specific ultra-high voltage substation, an analysis of the station's primary and secondary equipment was conducted. Utilizing operation and maintenance techniques such as infrared thermometry and X-ray inspection, the anomaly was localized. Subsequent de-energized disassembly inspection revealed the root cause: screws connecting the transition conductor to the contact support were not properly tightened. Under the influence of current and voltage, this condition gradually caused burning/arcing erosion on the contact surface. Concurrently, environmental temperature variations induced weak deformation in the vertical busbar section due to stress, collectively leading to the abnormal busbar current. This conclusion was substantiated through calculation analysis and experimental verification. Finally, recommendations for handling similar current abnormalities were provided.