Abstract: Considering the inherent deficiency of the Alford force model, a new comprehensive leakage flow mechanism on the clearance-excitation forces acting on turbine rotors is studied by taking both the influences of the radial and axial clearance variations on the leakage flow into account. The new mechanism considers the radial eccentricity and the axial pitch angle of turbine rotors. Based on the proposed mechanism, a nonlinear clearance-excitation force model of turbine rotors is developed, which reflects the radial eccentricity and the axial pitch angle of turbine rotors on one hand and embodies the mean radial and axial clearances on the other. A set of figures reflecting the relationships of clearance-excitation force to the eccentricity and pitch angle are obtained through numerical integration. The effects of the mean radial and axial clearances and the phase angle differences between eccentricity and pitch on the clearance-excitation force are discussed. The present model is proved to be effective by the experimental data available at present, and is of practical significance in the dynamical modeling of turbine rotor systems with the consideration of fluid-structure interactions.