Abstract: The stainless steel plate spring in GIS fractured during 200 cycles' operation test. The fracture causes of the plate spring were analyzed by macroscopic analysis, chemical composition analysis, fracture analysis, metallographic analysis and mechanical property test. The results show that the micro-defects on the surface of the plate spring, the grooves and inclusions in the microstructure, the corrosive environment containing chloride ions and the stress acted together and resulted in the stress corrosion cracking of the plate spring. Finally, preventive measures were put forward for the fracture causes of the plate spring.