The importance of thermal physical parameters to numerical simulation of hot forging was analyzed, and a simple experiment method to get equivalent thermal parameter was designed. Combining heat experiment and software,the parameters were deduced using the approximation method of simulated data and the measured data. Because the method ranks thermal interference of other factors in the experimental details, the measured parameters reliability and accuracy are higher. Taking rotor steel 26Cr2Ni4MoV as an example, the equivalent black degree coefficient was tested which is 0.250.30 in the forging interval from 1260 to 850℃ through the method, and the coefficient of the die steel loading equivalent heat transferring is 1.0 kW·(m2· K)-1.