Abstract: In this paper, the ABAQUS was used to build a finite element model of AlCoCrFeNi2.1 eutectic high entropy alloy formed by selective laser melting (SLM), and achieved the movement of Gaussian heat source through DFLUX subroutine compilation. The effects of process parameters on temperature field, microstructure, and mechanical properties were investigated by analyzing melt pool size, temperature change and liquid phase time. By simulating the size and morphology of the melt pool during the forming process of SLM, the variation law of the melt pool temperature field of AlCoCrFeNi2.1 eutectic high-entropy alloy prepared under different process parameters was obtained. Furthermore, based on the experiment, the microstructure and mechanical properties was studied, which was utilized to verify the reliability of numerical simulation results. The results indicated that both maximum temperature and melt pool size increase with laser power but decrease with scanning speed. In addition, cooling rate of the melt pool increases with a high laser power and a low scanning speed. When the laser power is 350 W, the scanning speed is 850 mm/s, the molten pool width is 138 μm, the depth is 61 μm, the width to depth ratio is 2.26, the obtained sample density is the highest 99.7%, the microhardness and tensile strength are 398.08 HV and 1529.5 MPa, respectively, and the comprehensive mechanical properties are the best.