Abstract: Fracture failure in small batches of pantograph torsion spring made of 0Cr17Ni7Al steel occurred in operation process. Fracture causes of torsion spring were analyzed by means of macroscopic inspection, chemical composition analysis, tne sile test, fracture analysis and metallographic examination. The results show that the fracture mode of pantograph torsion spring was fatigue fracture, and the fatigue source was located in surface of torsion spring. Scratch and drawing defects produced in drawing process of spring wire reduced the ability to bear complex stress, which finally led to fracture under the pantograph-catenary dynamic coupling alternating load.