The three-dimensional finite element model of the pantograph was established by the finite element software,and the propagation characteristics of fatigue crack at the end of the upper frame for the pantograph were studied by the fracture analysis software Franc3 D. The fatigue crack propagation life under normal temperature,atmospheric environment and corrosion environment were predicted. The results show that when a 2 mm surface crack has been produced at the end of pantograph upper frame,it will penetrate the pipe wall when it continues to expand to a surface length of about 15 mm. For normal temperature and atmospheric environment,the operation mileage of fatigue crack extension from 2 mm surface crack to 50 mm through crack is about 240 000 km. In the corrosive environment,the operation mileage of surface cracks extension to the same length is about31 900 km.