The T-slot milling cutters were proposed to use for the cutting of slots by aimed at the Carbon Fiber-reinforced Composites (CFRP). The slots milling testes of plain woven CFRP were done as a study object. The milling forces and the residual factor were analyzed. The experimental results show that the all cutting forces will decrease with the increased cutting speed vc, but cutting force Fx will increase gradually in feeding direction, when the cutting speed vc is more than 245 m/min. The residual factor Fb will be influenced greater by the feed speed vf as compared with the cutting speed vc. The residual factor Fb will decrease in average by 46.63%, with the increasing of the feed speed vf. The all cutting forces and the residual factor from up-milling are much smaller than ones form down-milling. The study results provide some technical guidance for the slots milling on CFRP.