Orthogonal cutting experiments of Fe-36Ni invar alloy are performed to investigate the influence of cutting conditons on adiabtic shear, which occurs in the process of chip formation of many materials. It is found that the cutting speed, cutting depth and rake angle all have influence on adiabatic shear and there is a critical cutting speed at which the adiabatic shear appears. By metallurgical observation, the critical cutting speed under different cutting depth and rake angles are given. A model based on linear pertubation analysis is used to predict the adiabatic shear critical ctting conditions of Fe-36Ni invar alloy. The comparison of prediction results and that of expriments shows that this prediction model is available.