Considering the interaction between the rigid body and liquid, a dynamic model for a liquid-filled rigid body was established based on the smoothed particle hydrodynamics (SPH) method. Firstly, the equations of motion of the liquid sloshing were derived in the non-inertial frame, and then the boundary conditions were considered by using the virtual mirror particle method. The absolute acceleration of each fluid particle was calculated to obtain the principal vector and moment of the inertial forces applied on the particle with respect to the rigid body center. D’Alembert’s principle was employed to calculate the simplified slosh force and slosh torque with respect to the rigid body center through the equilibrium equation. Then, by taking into account the kinematic constraint equations, the dynamic equations of the liquid-filled rigid body were derived. Numerical simulations of the liquid-filled rigid body excited by a harmonic force were carried out to verify the proposed model, and then the rigid-liquid coupling characteristics were analyzed for different parameters. The results indicated that the proposed dynamic model is suitable for not only small-amplitude sloshing but also large-amplitude sloshing.