Clamps are widely used in airplanes and are often used to fix various gas cylinders. The quality of the clamp affects the safety of flight. The fixing clamps for air-conditioning cylinders in a certain type of aircraft often suffer from fracture of the clamp body. Spot welding is used to weld the fractured location.Through stereo observation,fracture met-allographic observation,section composition analysis,low power test,and tensile test analysis,it is found that the clamp fracture is a corrosion fatigue fracture;the source of fatigue is at the junction of the clamp welding point and the heat-affected zone.When analyzing the welding quality,the metallographic insp-ection finds that there are small cracks at the junction of the clamp welding point and the heat-affected zone. The phenom-enon and causes of clamp fracture are studied and preventive measures are proposed.