As an important part of the fixture of simulation testing facility for wheel/rail, the shaft is subjected to the vertical loads and braking torque during the operation of the machine. The damage analysis of the shaft was presented in macro and micro level to investigate the damage mechanism of interference fit surface between the shaft and bearing. The results show that there exists the fretting damage on interference fit surface of the shaft due to the difference in the elastic deformation and the relative motion with reciprocating micro amplitude of the shaft and the bearing inner ring. And there exists serious nonuniform plastic deformation on interference fit surface，especially on the surface near the end of the brake. The analysis results provide the beneficial reference for the damage mitigation and prevention of the shaft.