To clarify the reliability of laser energy density as the basis for optimizing selected laser melting process, temperature field, melt pool size, and densification of selected laser melted specimens at different scan speeds with constant energy density were investigated through numerical simulation and experiments using cobalt-chromium alloy powder. The results show that the laser energy density is not a reliable parameter that affects the melt pool size and relative density of selected laser melted parts. In addition, the scanning speed of laser plays a crucial role in modulating the melting and solidification processes of the powder and melt pool size. When the laser energy density is the same, as the laser scanning speed increases, the melt pool size increases, and the density of the sample increases accordingly.