This study employs vacuum arc melting technology to fabricate FeCrMnAlCux (x=0, 0.5, 1.0, 1.5, 2.0) high-entropy alloys. The phase structure and microstructure of the alloys before and after corrosion were characterized using XRD, SEM, and EDS. The corrosion behavior of the alloys in 0.5M H2SO4 solution was analyzed through potentiodynamic polarization curves, EIS, XPS, and immersion tests. The results indicate that the addition of Cu promotes the formation of the FCC phase in the alloy, transforming it from a single BCC structure to a mixed BCC+FCC dual-phase structure. The high-entropy alloys with five different compositions exhibit a typical dendritic morphology. As the Cu content increases, the grains gradually refine, and the microstructure becomes more uniform. The FeCrMnAlCu1.5 high-entropy alloy has the highest corrosion potential (-0.363 V) and the lowest corrosion current density (2.148×10-5 A/cm2). The alloy"s corrosion resistance initially improves and then deteriorates with increasing Cu content. At x=2.0, the corrosion potential decreases to -0.394 V, and the current density increases to 2.865×10-4 A/cm2, yet its corrosion resistance is still superior to that of the alloy without added Cu. After corrosion, a composite oxide protective film forms on the cross-section of the alloy, effectively reducing its corrosion rate in 0.5M H2SO4 solution.