Specimens of MB15 magnesium alloy reinforced with SiC whiskers (SiCw/MB15) were fabricated using powder metallurgy route (PM). The influence of SiCw on the 150oC aging behavior of MB15 alloy was investigated by microhardness-testing, and SEM, TEM and tensile tests studied the influence of powder-mixing methods on the distribution of SiCw and the mechanical properties of SiCw/MB15. The results reveal that the double peaks exist in the age-hardening curves of both the unreinforced and the reinforced MB15 alloy, and the addition of SiCw can accelerate the age-hardening process of MB15 alloy apart from increasing its micro- hardness, moreover, the mechanical properties of SiCw/MB15 composite are significantly influenced by powder-mixing methods of PM.