In this study, the (FeCoNi)₈₆Al₇Ti₇ high-entropy alloy was prepared by selective laser melting (SLM), and then annealed at 780 °C. Both the as-fabricated and annealed (FeCoNi)₈₆Al₇Ti₇ high-entropy alloys were placed in 0.5 mol/L H₂SO₄ solution for electrochemical corrosion experiments to explore the corrosion performance of the high-entropy alloys under acidic environment. The open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and polarization curves of high-entropy alloys were measured by electrochemical workstation. It was found that the self-corrosion potential of annealed (FeCoNi)86Al7Ti7 high entropy alloy was higher, the self-corrosion current density was lower. Meanwhile, the capacitive reactance arc diameter was larger, the impedance value was higher, and the charge transfer resistance was larger in comparation with the as-fabricated alloy. X-ray photoelectron spectroscopy (XPS) was used to analyze the composition and content of the passivation film on the corroded surface. The results show that the oxide species on the corroded surface of the annealed high-entropy alloys are richer and the content is higher, and the stable passivation film is easier to be formed. The results show that annealing at 780 °C can significantly improve the corrosion resistance of (FeCoNi)₈₆Al₇Ti₇ high entropy alloys.