In this paper, a finite element model was developed to simulate the transient temperature field and the molten pool evolution for the selective electron beam melting(SEBM) additive manufacturing process of metals, which was examined against the analytical solution. With increase of the scanning speed, or increase of the beam radius, or decrease of the beam power, the maximum temperature decreases, and the length, width and the depth of the molten pool all decrease. The temperature field and the shape of the molten pool are not symmetrical about the center line of the scanning path, namely, on the side near the scanned zone, the heat affected range is greater, the temperature gradient and the molten pool size are smaller. From the cross section of the molten pool obtained by simulation, we can predict the overlapping rates of multi-bead and the fusion state of multi-layer under certain process parameters.