Oxide which affects the heat exchange process of the surface for forgings is inevitable during forging process. In order to provide the thermophysical parameters which are consistent with the actual production for the numerical simulation of the forging process of large forgings, a set heating and cooling tests of rotor steel 26Cr2Ni4MoV were carried out and the equivalent thermophysical parameters of 26Cr2Ni4MoV under the influence of think oxide were obtained by anti-analysis. The results show that the oxide skin has important influence on the thermophysical parameters of 26Cr2Ni4MoV. In the case without surface oxide, the emissivity is from 0.64 to 0.76, and in the case with surface oxide, the emissivity is 0.3. In the case without surface oxide, the heat transfer coefficient between forging and die is 1 N·s-1·mm-1·℃-1, and in the case with surface oxide, the heat transfer coefficient between forging and die is 0.105  N·s-1·mm-1·℃-1.