Abstract: Grain refining mechanisms of magnesium-zirconium alloys were investigated. Mg-Zr alloys were prepared and a mixture gas containing SF₆ was used for protection during melting and casting. The microstructure and properties of Mg-Zr alloys and the effects of strain, frequency, temperature as well as the addition of Zr on the damping capacity were studied. The damping capacity was validated with vibration attenuation experiment. The results show that zirconium is a potent grain refiner for magnesium alloys. The average grain size can be reduced to 30μm for Mg-0.45%Zr(mass fraction) alloy and the mechanical properties of Mg-Zr alloys can be dramatically improved with increasing zirconium content. It is also found that the damping capacity has almost no connection with frequency, but increases with strain, the loss factor reaches 5.3×10^-2 at a strain amplitude of 1×10^-4. The value of transfer ratio of Mg-Zr base is 1.88 and obviously less than that of ZM6 alloy base and LY12 alloy base.