The scaling effect of specific cutting energy is one of the most challenging problems in metal cutting. There is no consensus reached on the mechanism of the scaling effect, and the contribution of the cutting temperature on the scaling effect was rarely studied. Here the orthogonal cutting experiments under different initial temperature were conducted. It shows significant dependence of the scaling effect phenomenon on the temperature effect. The scaling effect phenomenon becomes more obvious at lower initial temperature. The finite element model of orthogonal cutting was further developed to study the contribution of temperature on the scaling effect. The results show that, there exists two temperature gradient zones near the ends of the primary shear zone along the shear direction. The length of the gradient zones are independent on the uncut chip thickness. The existence of the temperature gradient zones causes the average temperature in the primary shear zone to drop with decreased uncut chip thickness, which gives rise to the increase of flow stress, leading to the nonlinear increase of the specific cutting energy.