Predicting the microstructure during selective laser sintering (SLS) is of great interests, which can compliment the current time and cost expensive trial-and-error principle with an efficient computational design tool. However, it still remains a great challenge to simulate the microstructure evolution during SLS due to the complex underlying physical phenomena. In this work, we present a three-dimensional finite element phase-field simulation of the SLS single scan, and revealed the process-microstructure relation. We use a thermodynamically consistent non-isothermal phase-field model including various physics (i.e. partial melting, pore structure evolution, diffusion, grain boundary migration, and coupled heat transfer), and interaction of powder bed and laser power absorption. The initial powder bed is generated by the discrete element method. Moreover, we present in the manuscript a novel algorithm analogy to minimum coloring problem and managed to simulate a system of 200 grains with grain tracking using as low as 8 nonconserved order parameters. The developed model is shown to capture interesting phenomena which are not accessible to the conventional isothermal model. Specifically, applying the model to SLS of the stainless steel 316L powder, we identify the influences of laser power and scanning speed on microstructural indicators, including the porosity, surface morphology, temperature profile, grain geometry, and densification. We further validate the first-order kinetics during the porosity evolution, and demonstrate the applicability of the developed model in predicting the linkage of densification factor to the specific energy input during SLS. even sort of empirical knowledge [5,19,20]. There are already many computational works performed regarding the underlying physics during SLS, where powder-laser interaction [7,[21][22][23] and heat transfer [24][25][26][27] have been massively investigated. Apart from those, the microstructure evolution has also gained great interests since it is directly related to mechanical properties of the final products like tensile strength, ductility, and fracture toughness. Up to now, however, it still remains a great challenge to simulate the microstructure evolution if the influences from all aspects are considered. During scanning, there is drastic difference in the thermal conditions among particles due to different exposure to the laser beam. Some of particles may even partially melted during the process [5,28]. Therefore, binding mechanism for certain particle/grain may vary from the solid-state sintering to the liquid-state sintering, and even melting-solidification according to the intensity of its partial melting [8,[28][29][30]. For the same reason, very high temperature gradients and cooling rates also exist [7,31], which make the mechanism of grain coalescence and coarsening during SLS deviate from that in conventional isothermal sintering.In recent decades, the phase-field method has been utilized to simulate the microstructure evolution during sintering-...