Abstract: Using plasma arc additive manufacturing technology, the influence of different process parameters on the organization and properties of AlCoCrFeNi_2.1 eutectic high entropy alloy was studied by single control variable method, to obtain the optimization parameters of the additives, and to study the influence of different number of thermal cycles on the organization and properties of the additive thin-walled. The results show that when the melting current is 130 A, the melting speed is 5 mm/s, and the powder feeding rotational speed is 2 r/min, the deposited layer with no obvious surface defects, high molding coefficient and high hardness is obtained. As the deposited layers are stacked layer by layer, the bottom region has the highest number of thermocycling layers, which dissolves the BCC phase into the FCC phase and coarsens the tissue grain, resulting in the lowest hardness at the bottom and higher at the top. The average hardness of the additive is 326.64 HV_0.5 ± 2.04 HV_0.5. With the soft phase, the FCC phase, the grains become smaller and the content of FCC phase decreases from the bottom to the top, which leads to the gradual decrease in tensile strength and plasticity and a slight increase in yield strength. The mechanical properties of the longitudinal specimens are better than those of the transverse specimens, showing obvious anisotropy, and the tensile strength can be as high as 1131.17 MPa ± 34.39 MPa, the yield strength of 594.66 MPa ± 3.71 MPa, and the elongation at break of 16.47% ± 2.21%.