Mg-6Zn/1.5%SiC nanocomposites were successfully fabricated by ultrasonic cavitation-based dispersion of SiC nanoparticles in Mg-6Zn alloy Inch. As compared to un-reinforced Mg-6Zn alloy matrix, the mechanical properties of the nanocomposites including the tensile strength and yield strength of the Mg-6Zn/1.5%SiC nanocomposites were significantly higher; the good ductility of Mg-6Zn alloy matrix was retained. Nanoparticles were dispersed well though there were still some SiC microclusters in the microstructure. Also, the grain size of Mg-6Zn alloy was reduced considerably by the addition of 1.5%SiC nanoparticles.