To solve the problem of the cutting force performances in cutting SiC reinforced aluminium composites, SiCw/LD2 composite, 45 steel and aluminium alloy were turned using self-propelled rotary cutters and fixed circular inserts. The cutting forces were measured and analyzed using a Kistler dynamometer. The experimental results showed that the average value and the peak value of the radial thrust cutting force Fp using self-propelled rotary cutters were lower 30%-60% and 70%-80% than that of using fixed circular inserts respectively. In increasing the cutting speed, the cutting forces using self-propelled rotary cutters were fast reduced and the coefficient Kp of cutting force was less than one. With the increase of the cutting speed, the cutting forces using fixed circular insert were similarly reduced, but the coefficient Kp of cutting force was more than one. In increasing the feed rate, the cutting forces using fixed circular inserts will be rapidly increased and the coefficient Kp of cutting force was more than one. Contrarily, the increments of the cutting forces using self-propelled rotary cutters when increasing the feed rate was slowly increased and the coefficient Kp of cutting force will be rapidly changed from more than one to less than one. In machining the composites reinforced with SiC whisker of moderate or lower volume fractions, the self-propelled rotary cutters are found to be one kind of tools with low cost high cutting performance. Higher cutting speed and bigger feed rate should be adopted in machining.