Friction in the single point incremental forming (SPIF) process is the main factor affecting the surface quality and forming performance of the workpiece. In order to study the effect of process parameters on friction in SPIF, the contact area between the forming tool and the metal sheet was taken as the analysis object according to the principle of SPIF and the characteristics of friction in the forming process. The force status was analytically expressed under the condition of considering friction, and a correlation expression between the forming force and the friction coefficient was given. On this basis, the friction coefficient values under different process parameters were calculated through experimental force measurement, and the accuracy and validity of the obtained friction coefficient were verified by finite element simulation. Finally, the influence of the forming parameters on the friction coefficient and the prediction model of the friction coefficient were analyzed using the surface response method. The research results revealed that the increase of tool diameter or spindle speed helped to reduce the friction coefficient between the contact surfaces, while the increase of layer feed, feed rate, or forming angle increased the friction coefficient to different degrees. The results obtained in this work may provide a reference in theory and technology for improving the surface quality and formability of parts.