The microstructure morphology differences and element diffusion conditions of Al-Zn-Mg-Cu alloy alclad sheet with the thickness of 6.32 mm before and after bending were characterized and analyzed by micro-hardness testers, metallographic microscopes, scanning electron microscopes and matching energy dispersive spectrometers. The results show that after hot rolling compound treatment, the transition bonding interface area of Al-Zn-Mg-Cu alloy alclad sheet is flat and smooth without defects such as pores, voids and oxide inclusions. The transition interface is in a good metallurgical bonding state. The microhardness of alclad sheet gradually increases from the 1/2 position of aluminum coating along the thickness direction to the core material, and stabilizes around 200 HV. The concentration of main alloy elements in the matrix structure of alclad sheet shows a gradient trend at the transition interface. At the same time, after bending at 60°, 90°, 120°, 150° and 180°, no cracking is found between aluminum coating and core material. The bending performance of sheet is good, but the surface becomes rougher with the increasing of bending angle.