The dynamic model of journal and floating ring for a radial floating ring hydrostatic/hydrodynamic bearing was established when considering the floating ring mass.The stability criterion of the radial floating ring bearing was deduced using Routh-Hurwitz method.The stiffness and damping coefficients of a high speed floating ring bearing were calculated with finite difference method.The threshold speeds under different eccentricity were acquired,and the influence of floating ring mass on bearing stability was investigated.Results show that the influence of floating ring mass on bearing stability is increased when the increasing of mass ratio of float ring and rotor.The threshold speed is decreased when the floating-ring mass is considered,and with the increasing of eccentricity,the magnitude of change is increased first and then decreased.