A statistical model for torsional friction of plate-on-plate contact is constructed. The torsional responses including T–θ curves, proportion of slip asperities, and the radius of gross slip can be obtained from the model. The torsional friction response of monomer cast (MC) nylon against 316L stainless steel was calculated with this model and a torsional friction experiment of MC nylon against 316L stainless steel was performed to verify the model. The calculated T–θ curves exhibit different shapes under different torsional angular displacements. The calculations demonstrated that the torsional regime determined only through T–θ curves was inaccurate. The statistical results of asperities located at the torsional interface more directly reflected the torsional regime. The T–θ curves obtained from theoretical calculation and experiments are consistent in shapes, whereas the torque magnitude from the theoretical calculation is larger than that from experiments. When gross slip is indicated by the maximum torque on the T–θ curves, about 93% of the contact asperities were in a slip status rather than 100% and the gross slip radius in the whole torsional contact interface was about 3 mm.