SiC nanoparticles (40nm) reinforced metal matrix composites (MMCs) were made by a common stir casting technique in two different preparation processing routes. In the first route, the coated ceramic powder was prepared using electroless plating to coat SiC nanoparticles by Cu. In the second route, Cu and SiC nanoparticles were fully mixed by high energy ball milling, and then SiC nanoparticles were embedded in Cu to form a “jujube-cake” structure. In both cases the average particles size were 0.2μm. The SiC nanoparticles enhanced A6061 alloy matrix composites were made by stir casting, and as-cast microstructures were studied by means of optical microscopy (OM) and scanning electron microscopy (SEM). The results show that in the first route, the Cu off and the slagging reaction occurs to form a mixture at the upper part of the ingot by a vacuum melting and the ingot central also has a large number of pores, only the lower part of the ingot organization is uniform. The second route can make better uniform composites.