The edge shape of milling insert has important influence on the heat loading and mechanical loading during metal cutting. The optimization of edge-shape parameter for curve-edge milling insert based on evaluation criteria of thermal-mechanic coupling field was carried out in order to improve the thermal-mechanic coupling field and to raise lifetime and production rate of milling insert. A new edge shape function was obtained. The curve-edge milling insert was designed driven by the edge function. The coupling field of milling insert has obvious improvement by finite element analysis (FEM). The maximal equivalent stress and displacement in cutting deformation area decreased by 17.2% and 15.7% respectively.