The microstructure of as-cast Mg97Zn1Y2 with or without solid solution treatment was analysised by OM and SEM.Meanwhile, phase analysis was carried out by EDS and XRD. After solid solution treatment, LPSO phase grow up,turning into continuous distribution in Mg97Zn1Y2.Through damping testing, it was found that the damping capacity of Mg97Zn1Y2 was declined after solid solution treatment.The damping-temperture specturm of the as-cast Mg97Zn1Y2 with or without solid solution treatment was also analysised. There are two internal friction peaks:damping peak P1 located between 150 ℃ and 250 ℃ and the peak is very wide, which is caused by the dislocation mechanism.Meanwhile, the damping peak P2 is near the 350-500 ℃, which is preliminary considered as grain boundary internal friction peak.