Solidification behavior and as-cast microstructure of permanent mould casting Mg-10Zn-2Al alloy were investigated by optical microscope（OM）,scanning electron microscope（SEM）,X-ray diffraction（XRD）and differential scanning calorimetry（DSC）.Meanwhile,phase transformation during solidification process was approached with the help of DSC analysis and Mg-Zn-Al ternary liquidus projection phase diagram.The results indicate that as-cast microstructure of the alloy is composed of primary α-Mg phase,Mg32（Al,Zn）49 and MgZn phase,in which continuous or semi-continuous skeleton Mg32（Al,Zn）49 phase is uniformly distributed in interdendrite and along grain boundaries.The liquidus temperature and solidus temperature are 609.4℃ and 300.0℃,respectively,which makes a wide solidification range of approximately 309.4℃.In addition,the second phase transformation starts at 332.2℃ and ends at 300.0℃.