Abstract: The air condition compressor springs broke during the durability test of the system. Fracture analysis, metallographic examination, chemical composition analysis and hardness test were used to analyze the fracture causes of the springs. The fatigue strength of the springs was checked and the improvement of the shot peening process was also studied. The results show that the maximum shear stress of the springs in practice was higher than the allowable shear stress of the material. The safety factor of the springs was insufficient under cyclic loading, and fatigue fracture finally occurred. The reliability of springs could be improved by shot peening process. The springs treated by shot peening with φ0.2 mm steel balls had the best surface morphology and the highest fatigue life.