Abstract: To address the challenges in locating multiple or cross-region composite faults, this paper presents a rapid diagnosis method based on the coordination of internal/external zone criteria and setting simulation。 The approach is demonstrated through a case of composite short-circuit fault between phases BC of #1 main transformer and phases AB of #2 main transformer during parallel operation in a 110kV substation. Without complex modeling, the method utilizes existing fault recording data and grid setting calculation models to accurately identify composite faults。Compared with traditional fault record analysis, the diagnosis time is greatly reduced, significantly improving repair efficiency。This method can be seamlessly integrated into existing protection information systems and has broad application potential。