ZL101 alloy was modified by using mechanical stir casting process with an addition of rare-earth Yb at the mass fraction of 0-0.9%, for investigating the effect of Yb content on the microstructure and corrosion resistance of ZL101 alloy. The results show that with the addition of rare-earth Yb at a mass fraction of 0.6%, ZL101 alloy has its α-Al phase changed from coarse dendritic structure without modification to spheroidal dendrite with fine size, regular shape and regular arrangement, also the eutectic Si phase changed from the coarse long strip and needle sheet to the granular and short rod. It is shown that Yb reacts with Al substrate to form Al₃Yb rare-earth phase with long strip structure. With the addition of Yb at 0.6%, ZL101 alloy has its corrosion rate at 13.25 mg/(cm²·d), 37.23% lower than that before the addition of Yb. It can be seen from the corrosion surface observation that increasing Yb content leads to gradual decrease in the number of corrosion products and pits on the corrosion surface of the alloy.