Abstract: The addition of Cu element in Al-Zn-Mg alloy can improve the corrosion resistance of the alloy. At the same time, Cu element can also reduce the stress concentration at grain boundaries. The electromagnetic stirring casting technology was used to prepare Al-Zn-Mg-Cu alloy samples with different Cu contents. By using X-ray diffraction, scanning electron microscopy, hardness tester and intergranular corrosion（IGC） detection methods, the effect of Cu content on the microstructure and properties of electromagnetic stirring casting Al-Zn-Mg-Cu alloy was studied. The results show that with the increase of Cu content, the content of Al₂ Cu and Al₂ CuMg phases increase, and non-equilibrium eutectic phases appear in the microstructure, resulting in an improvement in hardness. When the copper content increases from 2.0 wt% to 3.0 wt%, the hardness of the alloy increases from 122.7 HV0.3 to 127.2 HV0.3, and the hardness increases by 3.6%. And the corrosion resistance first increases and then decreases. When Cu content is 2.5 wt%, the aluminum alloy has the best corrosion resistance.The analysis shows that there is more Mg Zn₂ phase in the alloy, while the content of Al₂ Cu and Al₂ CuMg phases is relatively low. The large presence of Mg Zn₂ phase makes the alloy have good corrosion resistance, which significantly improves the corrosion resistance of the alloy.