Zinc-aluminum-magnesium coatings possess excellent corrosion resistance, and electroplated zinc-nickel coatings are also a type of high-corrosion-resistant coating. However, there has been no research on the corrosion behavior after nickel electroplating on the surface of zinc-aluminum-magnesium coatings. Nickel was electroplated onto a zinc-aluminum-magnesium coating using electroplating technology to obtain a ZnAlMgNi plating. Scanning electron microscopy was used to analyze the surface microstructure of the samples, glow discharge optical spectroscopy was used to analyze the thickness of the nickel coating, and polarization curve and AC impedance spectroscopy techniques were used to evaluate the effect of the nickel coating on the corrosion resistance of the zinc-aluminum-magnesium coating. The analysis results show that under different electroplating process conditions, the thickness of the nickel layer on the surface of the zinc-aluminum-magnesium coating is 50–200 nm. Polarization curve analysis shows that when the nickel coating is 50 nm thick, the corrosion potential of the sample increases from −1.016 V vs. SCE to −1.005 V vs. SCE, the corrosion current density increases from 14 mA/cm2 to 17 mA/cm2, and the polarization resistance decreases from 886 Ω·cm2 to 693 Ω·cm2. When the thickness of the nickel coating is 200 nm, the corrosion potential of the sample further increases to close to −1 V vs. SCE, the corrosion current density increases to 57 mA/cm2, and the polarization resistance decreases to 289 Ω·cm2. Compared to the zinc-aluminum-magnesium coating, the corrosion resistance of this ZnAlMgNi plating shows a significant decline.