There are wide and efficient military application prospects for the vertical and/or short take-off and landing (V/STOL) aircraft. A dynamic model of V/STOL aircraft accurately reflecting the dynamic characteristics in flight simulation should be built for research on its complex flight control. By employing the principle of linear superposition and combining the mechanism modeling and empirical formula, a complete propulsion/aerodynamic force and torque model was built considering the impacts of the changing rate of gas mass flow, nonlinear and unsteady dynamic characteristics at high angle of attack, unpowered ground effect, and jet-induced effect. By applying this model, the 6-DOF nonlinear mathematic model was deducted according to the principle of rigid body dynamics and kinematics. Finally, simulation analysis provided the dynamic changes of V/STOL aircraft caused by ground effect, the jet-induced effect and the unsteady dynamic characteristics of the delta wing. Results indicate that the effect of ground effect on the dynamics of V/STOL aircraft can be ignored, while the jet-induced effect in near ground flight leads to greater lift loss that increases with the decreasing flight altitude. The unsteady dynamics of V/STOL aircraft which is derived from the hysteresis effect caused by the change of angle of attack is significant at high angle of attack and small airspeed. This model has the characteristics of clear physical meaning and simple calculation, can reflect the dynamic characteristics more accurately, and can provide help for model simplification and flight control system (FCS) design in different flight modes for the V/STOL aircraft.