Abstract: High-speed milling tests were carried out on the SiCp/2009Al composites with different volume fractions of SiC particles using polycrystalline diamond (PCD) tools through the method of orthogonal experiments design. The empirical formulas of tool life and surface roughness were established. In order to obtain lowest unit cost, lowest surface roughness and longest tool life, genetic algorithm had been used to optimize the processing parameters. The results show that volume fraction φ of SiC particles had the most remarkable effect on tool life, cutting speed v was the second significant factor, fz and radial aw had no significant effects on tool life. The significance of factors for effecting surface roughness was in sequence of fz, v and aw. The optimized process parameters was v=760 m·min-1, fz=0.08 mm, aw=3 mm, φ=17%.