Abstract: AlCo_1.2Cr_0.8FeNi_2.1 eutectic high-entropy alloy (EHEA) was designed and prepared by vacuum medium frequency melting furnace, and the effect of solution treatment on its microstructure and corrosion properties was studied. The crystal structure and microstructure of AlCo_1.2Cr_0.8FeNi_2.1 EHEA were characterized by XRD, SEM and EDS, and the corrosion properties of the alloys in 3.5 wt%NaCl solution at room temperature were tested by electrochemical workstation. The results show that the as-cast AlCo_1.2Cr_0.8FeNi_2.1 EHEA exhibits a typical eutectic structure composed of FCC and B2 phases. After solution treatment at 800 ℃ for 1h, the alloy does not undergo obvious phase transformation and has good high temperature stability. However，needle-like precipitates appear in the alloy after solid solution treatment at 900 ℃ and 1100 ℃, and the B2 phase which is rich in Al and Ni elements precipitates in FCC phase. After heat treatment at 1200 ℃, the precipitated phase disappears, and the structure and element distribution are more uniform. Besides, the alloy after solution treatment at 1200 ℃ for 1 h has higher corrosion potential, lower corrosion current density and larger polarization resistance, showing the best corrosion resistance.