High current pulsed electron beam (HCPEB) surface modification processisn on steady state temperature field with internal heat source, ANSYS software was applied to simulate the temperature field. Pure magnesium was used as experimental materials, and HCPEB device was used to carry out 10 times pulse irradiation on the sample surface. One dimensional heat source physical model of HCPEB surface modification process was established. And on the basis of experimental and theoretical, numerical simulation of the temperature field evolution during electron beam modification was carried out. Simulation results show that physical model is consistent with experimental results.