In order to find optimal cutting parameters of carbon steel C45, the optimizing experiment of the cutting parameters in High-Speed Machining based on Taguchi method is presented in this paper. High-Speed milling experiments were designed with high-speed machining tool and surface roughness tester as the equipment. The cutting speed, the feed per tooth and the cutting depth were selected as the cutting parameters while the surface roughness was taken as the criterion. The mean surface roughness and SNR of every factor at different levels was obtained. The effects of these parameters on the surface roughness have been researched by means of the analysis of variance, and then the optimal cutting parameters were found.