According to the actual experimental condition of the scanning electron beam welder, a 3-D finite element model(FEM) model of the temperature field for the electron beam quenching of ductile iron QT600-3 was established by using ANSYS parametric design language. In the course of analysis, the heat transfer theory was applied. The temperature relativity of the thermal physical parameters, the phase transformation and thermal radiation were considered. The size of the hardened zone was calculated and experimented. The results show that the obtained experimental results show a good agreement with the simulation results. It indicates that the established numerical model is correct and reliable. The model provides a guide for studying the rule which it is heating and solidifying process of electron beam surface quenching. And the FEM model can be well used to obtain and optimize the processing parameters.