Abstract: SiC particles reinforced Mg-2.1%Zn-0.7%Zr alloy composites were prepared by stir casting.The damping capacity of the matrix alloy and the composites varying with amplitude and temperature was investigated by LMR-1 low-frequency torsion pendulum system.The results show that the damping capacity of the composites at room temperature decreased slightly as the increase of the SiC content.The internal friction value of the composites was the same of that of the matrix alloy when the temperature was in the range of 25-250℃.A contrary result could be obtained at the temperature higher than 300℃.The damping mechanism of the matrix alloy and the composites could be explained by G-L theory.