In all machining methods, surface roughness greatly influences the working ability and the life of parts. Besides, material removal rate (MRR) is the parameter that reflects machining productivity. Low surface roughness and high MRR values are ideal for most of the methods. This article presents a research on multi-objective optimization of turning process. The material used in the experiments is SCM440steel. And Taguchi method is applied to design an orthogonal array (L27), in which five parameters are selected as the input of testing process including cutting tool material, tool nose radius, spindle speed, feed rate and depth of cut. In addition, Reference Ideal Method (RIM) is applied to identify the value of the input parameters to achieve the minimum surface roughness and the maximum MRR. Accordingly, in order to obtain the maximum MRR and the minimum surface roughness at the same time, it is necessary to use TiN coated cutting tool, with the tool nose radius of 0.6 mm, the cutting speed of 94.25 m/min, the feed rate of 0.16 mm/rev, and the depth of cut of 0.5 mm. Impact of input parameters on output parameters is also analyzed in this study.