An analytical model for contact area and contact stress considering the loading history in incremental sheet forming (ISF) was established. Then, by integrating with the directional characteristics of friction force and horizontal force in the process, a friction test method reflecting the forming characteristics of ISF was proposed. Friction coefficients during the forming processes of parts with different wall angles were measured under various plane curves, process paths, and lubrication conditions. Furthermore, the accuracy of the analytical model, as well as the measured friction coefficients and their variation trends, was verified through comparative analysis with experimental results, simulation data, and outcomes from other existing models. The results indicate that the influence of the plane curve characteristics and process paths of parts on the friction condition is not significant. Under the lubrication conditions of L-HM46 oil, MoS₂ grease, graphite powder, and dry friction, the friction coefficient shows a gradually increasing trend. Notably, when the wall angle is ≤40°, the friction coefficient remains relatively constant; however, when the wall angle exceeds 40°, the friction coefficient increases progressively.