Superplastic behavior was investigated using an extruded Mg-Zn-Y alloy with the dispersion of the quasicrystal phase particle in fine-grained matrix. Tensile tests showed that the low temperature superplasticity was behaved at a temperature of 473 K and maximum elongation was 462 % at 573 K in 1 10-5 s-1. The deformed microstructure observation showed that the dominant deformation process was grain boundary sliding. The present alloy also demonstrated a high possibility for secondary forming, such as superplastic forge forming. Furthermore, the forged alloy had a homogeneous microstructures, no mechanical anisotropy and uniform micro-hardness properties in any portion of a forged product.