Abstract: To investigate the influence of process parameters on the forming process and quality during selective laser melting (SLM), 316L stainless steel powder was selected as the material, and controlled experiments of SLM-formed 316L stainless steel were conducted. On this basis, numerical simulations were carried out. A powder model with a single-layer thickness of 40 μm was established using the discrete element method (DEM), and computational fluid dynamics (CFD) was performed to simulate laser-induced powder bed melting processes. Finally, cellular automaton (CA) was used to simulate the microstructure of the melting region based on the simulated temperature field. The results showed that when the laser heat input was in the range of 136.4 ~ 250.0 J/m, the single-track quality was higher. When the scanning interval was 70 μm, the laser heat input should not be lower than 181.8 J/m. The microstructure simulation results showed that the grain size in the molten pool was closely related to the laser power and scanning speed. In the range of reasonable laser heat input , when the combination of process parameters was powder thickness of 40 μm, scanning interval of 70 μm, laser power of 200 W, and scanning speed of 1.1 m/s, the grain size in the molten pool microstructure was the smallest. The thermal fluid flow model and microstructure evolution model used in this paper could accurately predict the SLM forming results at different scales and provide guidance for the optimization of process parameters on the basis of experiments.