The dynamic stability of Rayleigh groove seal of liquid rocket engine is affected by structural parameters.A three degree of freedom perturbation model of Rayleigh groove liquid lubricated mechanical seal was established.The steady and dynamic Reynolds equations were solved by finite element method and small perturbation method.The effects of structural parameters on dynamic characteristic coefficients and seal stability were analyzed.Results show that the change of the same structural parameter of Rayleigh groove has different effects on dynamic characteristic coefficients.With the increase of groove number and shallow groove width and the decrease of inner radius of shallow groove,the axial stiffness coefficient and angular stiffness coefficient become larger,while the angular coupling stiffness coefficient and dynamic damping coefficients get smaller.The dynamic characteristic coefficients decrease with the increase of deep groove width and shallow groove depth.The change of deep groove depth has little effect on dynamic characteristic coefficients.The Rayleigh groove seal does not suffer axial instability,and the phenomenon of “half frequency oscillation” exists in angular direction.The decrease of groove number and shallow groove width and the increase of shallow groove depth are easy to cause angular instability of Rayleigh groove seal.