On the basis of analyzing the cutting edge structure and cutting edge radius measurement of high-speed insert, thermal - mechanical coupling finite element method (FEM) is used in this paper, to obtain the effect law of different cutting edge radius on the mechanical-thermal distribution of high-speed cutting TiAl6V4. At last, cutting experiments are carried out to verify FEM results. There is a clear exposition of the intrinsic reason why the cutting edge radius has influence on the mechanical -thermal distribution of high-speed cutting process. The results indicate that the experimental results have a good agreement with FEM; with the cutting edge radius increases, cutting force increases; cutting temperature is not monotonic, but there exists an optimum edge radius that makes temperature lowest; cutting edge changes the plastic flow of materials around tool tip and broaden plastic deformation zone. The cutting edge radius has a greater impact on equivalent stress.