The work aims to improve the service life of carburied& quenched shaft. The hole on the key part of the carburied& quenched shaft was treated by ultrasonic impact. The microstructure, hardness and residual stress after treatment were analyzed by electron microscope, hardness tester and finite element simulation. The material became hardened obviously in the hole processing area and then formed the gradient hardening layerwhich reached the thickness of 80 μm including 60HRC surface hardness. The residual stress on the hole by ultrasonic impact was measured and the minim value was ?374 MPa and the maximum value was ?530 MPa. After the above ultrasonic impact treatment, the average residual stress of samplewas ?50 MPa. The finite element method was used to simulate the residual stress distribution of the depth along the axial, and the residual compressive stress layer depth was about 1.4 mm, the residual stress was ?891 MPa, and the average residual stress in the fatigue dangerous spot was about ?760 MPa. The third principal stress on the edge of the gear shaft near the hole was basically along the axis of the gear shaft. After the carburied& quenched shaft hole is treated by ultrasonic impact, the hardening layer is formed in the hole angle and the residual stress can be generated. Therefore, the above treatment can effectively reduce the fatigue load caused by the working stress.