Abstract: AlCoCrFeNi_2.1 eutectic high entropy alloys (EHEAs) were prepared by laser powder bed fusion (L-PBF) technology, the effects of L-PBF parameters on the formability of the alloys, the unique duplex microstructures and the mechanical properties of the formed specimens were investigated. The results show that, combining the L-PBF process parameters, AlCoCrFeNi_2.1 EHEAs indicate the highest densification up to 99.38% and the lowest different surface roughness when volumetric energy density(VED) VED=119 J/mm³. The AlCoCrFeNi_2.1 EHEAs printed by L-PBF consist of FCC and BCC/B2 phases, the particulate B2 phase diffusely distributes in the BCC matrix. As a result of changes in cooling rate and interlayer heat transfer during solidification, eutectic lamellar structures, columnar crystals and cellular crystals coexist at different locations in the solidification melt pool. The microhardness of AlCoCrFeNi_2.1 EHEAs Printed by L-PBF is closely related to the forming accuracy, and the maximum hardness of VED 119 sample is 425 HV, the tensile strength is 1127 MPa and the plasticity is 14.1%. Due to the deformation incoherence between FCC and BCC/B2 phases, the flat phase boundary limits the dislocation slip and achieves a good match between strength and plasticity.