Considering the influence of matching of process parameters in selective laser melting (SLM) on forming quality, we choose three laser powers and conduct experiments at different scanning speeds and scan modes. The effect of laser power on the morphology of molten pool and residual stress is studied. Results show that an increase in the laser power leads to a corresponding increment in residual stress on formed parts and size of the molten pool. The main reason is that the heat flux density increases with the increasing laser power, the temperature gradient increases under the same thickness and cross section, and the temperature of the molten pool and its size increase. This results in a large interphase angle between crystal faces and large spacing between grain boundaries of different formed parts. It also results in excessive residual stress after cooling and solidification of the formed part corresponding to great thermal stress. Therefore, the thermal and residual stresses can be decreased by rationally selecting and matching the process parameters. Consequently, high-quality SLM parts can be produced.