The microstructure and macroscopic cracks of five twin-roll cast Al-Zn-Mg-Cu alloys strips with various Zn contents (3.5 wt pct, 5 wt pct, 6.5 wt pct, 8wt pct, and 10 wt pct, marked as Zn3.5, Zn5, Zn6.5, Zn8, and Zn10, respectively) were investigated. The results showed that the macroscopic cracks of strips decreased in numbers as the Zn content decreased from 10 wt pct to 5 wt pct, while this decrease was inhibited as the Zn content continuously decreased from 5 wt pct to 3.5 wt pct. The microstructure sustained a transition from columnar crystals to equiaxed crystals along the surface to the center of the cast strip. The center segregation band of the cast strips became wider and the non-equilibrium coarse eutectic phases increased in amount as the Zn content increased in these Al-Zn-Mg-Cu strips. Unsolidified liquid phases and holes appeared in the microstructures of strips of high Zn content.