The effect of fabrication conditions (initial thickness reduction ratio during rolling) on the mechanical properties of Mg-Zn-Y(-Mm) alloys has been investigated in the present study. Greater grain refinement in Mg-Zn-Y(-Mm) alloys due to dynamic recrystallization (DKX) can be achieved under higher initial reduction ratio of 10% than that of 5%, in spite of same total reduction ratio of 90%. The alloys rolled under high initial reduction ratio exhibit better mechanical properties since the grains are refined more effectively. The gap between the critical resolved shear stresses on the basal slip system and on the secondary slip systems becomes smaller with the increase of initial thickness reduction ratio. The wrought Mg-Zn-Y(-Mm) alloys exhibit a better combination of mechanical properties than AZ61 alloy.