Abstract: Two coated carbide inserts with the same geometric structure but different materials were used to turn T800H bar of typical carbon fiber reinforced composites. The cutting load and tool working state are monitored by multicomponent mechanical sensors, pressure sensors and high-speed cameras in turning process. The characteristics of machined surface and chip morphology were observed and analyzed by optical scanning system and digital microscope system. Experiment shows that:When turning carbon fiber reinforced composites, each tool has a critical cutting speed v_cr. Under the conditions of the same feed f and the constant cutting depth a_p, the cutting speed v_c has little effect on the machined surface quality of the workpiece. Besides, the better quality of machined surface can be obtained by turning carbon fibers with higher hardness tools.