The finite element simulation is used to investigate two different Z-shaped scanning paths parallel to the long and short sides. Considering the effects of heat conduction, heat convection, heat radiation, and temperature on the thermal properties of alloy powder materials, the finite element model of the transient selective laser melting (SLM) temperature field is established. Then, the established model is compared with the experimentally measured residual stress data and metallographic diagram. It is determined that in the SLM process, the temperature field formed by short-side scanning is more uniform; the temperature standard deviation, the temperature gradient, the residual stress, and the porosity of the formed part are smaller than those in the long-side scanning. During the scanning process, the temperature gradient at the boundary point of the scanning region is greater than that of the scanning region, and the residual stress peak appears at the boundary of the formed part. By preheating the substrate, the temperature field can be more uniform, and both the standard deviation and the gradient of the temperature field can be reduced. Therefore, the residual stress and the porosity of the formed part are reduced, and the forming quality is improved. The investigation of the influence of scanning path on the temperature field provides the reference for the improvement of the SLM technique.