Abstract: The flocking spring supporting the backdoor of a car fractured during its service. The fracture causes of the flocking spring were analyzed by macro and micro fracture morphology analysis, chemical composition analysis and corrosion product energy spectrum analysis. The results show that the flocking spring fracture was caused by stress corrosion cracking which occurred under the joint action of stress and corrosive environment. The main reason for the stress corrosion cracking of the flocking spring was that the used lubricating oil contained corrosive element chlorine. It is recommended to use regular brand and quality-assured lubricating oil for subsequent use.