Abstract: Liquidus and solidus temperature of Mg-6Gd-3Y-0.4Zr-2Zn magnesium alloy were determined by means of differential thermal analysis, and semi-solid stirring was carried out at 610.5-642.5 ℃. The effect of semi-solid stirring on microstructure of the magnesium alloy was studied, and compared with the microstructure of the magnesium alloy without semi-solid stirring. The results show that, comparing with the microstructure of the magnesium alloy without semi-solid stirring, the grain size of the alloy with semi-solid stirring gets refined and spheroidized, meanwhile, the continuous network structure of second phases had a tendency to discontinuousness.