High speed milling tests were performed on the SiCp/2009Al composites to investigate the cutting forces by using PCD tools in the speed range of 600-1200m/min. The results showed that the peak value of the cutting force Fy (in the tool radial direction) was in the range of 700-1450N under the present cutting condition. The maximum amplitude of cutting force vibration in the tool radial direction can reach 700N. Cutting forces increased with increasing feed rate or radial depth of cut and decreased with increasing cutting speed. Negative rake angle and relatively large tool nose radius were recommended as far as cutting forces was concerned. Materials with higher volume fraction or smaller reinforcement particle size had the bigger cutting forces. T6 heat treatment can increase the cutting forces significantly but the using of coolant can decrease the cutting forces evidently.