From the L27 specimen, three indicated specimen’s parameters are chosen and has been simulated to analysis the relation between temperature and surface roughness. Figure 5.9 shows results of single layer simulations. The maximum temperature varies with time and the simulation results are plot in figure 5.10, figure 5.11, figure 5.12. The maximum temperature rises rapidly when the laser starts to heat the powder layer, and reaches to the temperature around 3200 K, 3100K, 4200K separately. The maximum temperature of crests elevates gradually till the equilibrium of the energy balance. The valley in the plot appears when the laser stops to heat the powder layer and starts to heat the next scanning track. The simulation result shows that the maximum temperature around vaporing temperature of the material has the better surface roughness. The worst surface roughness of specimen appears when the maximum temperature exceeds much more than the vaporing temperature. Crests in the figure 5.10 and 5.12 are lower than previous crests which is because the laser beam in the last path is part out of the observing region, and only parts of energy have been obtained.