From the L27 specimen, three indicated specimen’s parameters are chosen and has been simulated to analyze the relation between temperature and surface roughness. Table 5.6 shows the simulation result of the single layer, with increasing molten tracks, the temperature gradually increased to 3.73×〖10〗^3 K, which is at the 0.012 s of scanning time, the total scanning time is 0.022 s. The reason that the temperature stops climbing is because the rate of energy obtained from the laser and the rate of energy lost from conduction, convection and radiation achieve to a balance state.