There are serious problems in surface quality of the mided SiC_p/Al composites. The milling tests on SiC_p/Al composites were conducted with cemented carbide coating tools. Through single factor experiment, the article investigated the influence of cutting parameters on surface roughness.The results suggest that the surface roughness increases at first, then decreases with the increase of cutting speed, and increases with the increase of feed, radial cutting depth and axial cutting depth. The machined surface quality could be improved by using high cutting speed, low feed and the radial cutting depth equal or less than 4mm.