Panel mold has the characteristics of complex shape, high hardness and multi hardness stitching. In the process of machining, the tool load is unstable, the tool temperature is too high and the cutting tool is easily worn out. Thus the surface quality of the die and the service life of the tool are reduced. In order to reveal the milling mechanism, a threedimensional finite element simulation model for the milling process of convex surface splicing dies was established and the 3D finite element simulation method is used to study the milling process of the convex surface splicing die. First, the constitutive parameters of the material are fitted by the quasi static test and the Hopkinson pressure bar test to ensure the accuracy of the simulation results. Secondly, a three-dimensional thermal coupling simulation model of the convex surface splicing die milling process is established. Finally, the changing characteristics of force and temperature during the milling process of the convex surface splicing die are studied through simulation results. The research results provide theoretical support for mold of aerospace products milling technology and tool structure design.