The nonlinear and multi-factor-dependent characteristics of the hydrodynamic forces acting on the aft body of a supercavitating vehicle are investigated using computational fluid dynamics (CFD). The CFD model of natural supercavitating flow is first verified and validated upon the supercavitating flow around a cavitator in the shape of a circular disk. Then the model is used to simulate the supercavitating flows over a typical supercavitating vehicle model at different cavitation numbers σ and angles of attack (AOA) α. By analyzing the supercavitating flow patterns and hydrodynamic force curves, the hydrodynamic characteristics of the aft body and their forming mechanisms are revealed: (a) The normal force and pitch moment are mainly generated by the pressure difference between the windward side and leeward side of the cylinder section caused by asymmetrical reattaching of the supercavity. (b) The hydrodynamic coefficients depend on both σ and α nonlinearly. Free AOA αfr and critical AOA αcr are identified to model the nonlinearity of hydrodynamic force about AOA. (c) For the designated model, αfr and αcr depend on supercavitating flow patterns determined by σ. The simulation results and conclusions would be beneficial for more accurate dynamic modeling and control simulation for supercavitating vehicles.