Abstract: As a typical thin-walled casting, the end cover of light truck gearbox is mainly processed by milling. In order to make the flatness of the end cover meet the requirements after milling, it is necessary to accurately obtain the residual stress on the surface of the end cover after milling. The finite element models of gearbox end cover and cemented carbide end mill are established respectively. Based on HyperMesh software and ABAQUS software, the dynamic simulation model of milling is established to study the size and distribution of residual stress on the surface of end cover after milling. The results show that the maximum residual stress in the feed direction of the tool is 465 MPa, and the average stress is 156 MPa. The residual stress of the workpiece milling surface along the feed direction reaches the maximum near 550 mm, and then shows a regular distribution. The maximum residual stress of the feed slot appears at the inner edge of the end cover is 458 MPa, and the stress gradually decreases from the inside to the outside. The maximum longitudinal depth of the feed slot appears on the surface of the end cover at 436 MPa, and the stress gradually decreases along the depth direction. The results and conclusions of this paper provide a finite element modeling basis for the flatness control of the gearbox end cover milling.