The microstructure and texture evolution of Mg-xAl-1Zn-1Y-0.1Mn alloys are systematically analyzed. There is no effect of Al addition on grain refinement in the Mg-1Zn-1Y-0.1Mn alloy, but the addition of 0.5 wt.% or more Al element dramatically changes texture from a weak texture to a strong basal texture. The predominant second phase particle of Mg₃Zn₃Y₂ phase in the Mg-1Zn-1Y-0.1Mn alloy changes to Al₂Y phase by the addition of only 0.1 wt.% Al element, and the concentrations of dissolved Y element in the 0Al, 0.1Al, 0.3Al, 0.5Al and 1Al alloys are 0.50, 0.31, 0.23, 0.15 and 0.06 wt.%, respectively. Although the 0.5 wt.% or more Al-added alloys have higher Schmid factor for prismatic 〈a〉 slip than the 0.3 wt.% or less Al-added alloys, the lower Al containing alloys show much higher activity of prismatic 〈a〉 slip than the higher Al containing alloys. It demonstrates that the addition of high amount of Al element in Mg-Zn-RE alloy dramatically decrease the dissolved Y element, resulting in a significant deterioration of activity of prismatic 〈a〉 slip and consequently a poor formability at room temperature.