The lives of the two CERMETS cutters were investigated when turning 45carbon steel in the same cutting condition. The effect of tool orthogonal clearance on tool life was also researched in this paper. The results of the experiment were indicated as: the cutting performance of Nano TiN modified TiC-based CERMETS cutters was obviously superior to that of ultra-fine Ti(C, N)-based CERMETS cutters. And the length of cutting path of the two cutters was longest with the tool orthogonal clearance of 3-4°.