This paper proposes a numerical cutting model with the FEM to simulate the temperature field at the contact zone on the tool rake face. The analysis of the tool rake face temperature in orthogonal machining is studied based on heat transfer theory and calculus of variation. Then, the FEM simulation results of the temperature field on the rake face in various cutting speeds and the cutting speeds vs peak temperature curves are given. The results show that the highest temperature of the tool surface is located at a distance nearby the tool tip, and the higher cutting speeds can increase the tool rake face temperature obviously. In addition, the workpiece materials have a great effect on the peak temperatures at the rake face. Therefore, this study is helpful to investigate tool wear mechanism and optimize the machining parameters for the metal cutting processes.