Abstract: Based on the turbulent bulk flow theory, Moody wall friction coefficient equation, and our previous work, the first order perturbation equations of non linear governing equations of the large gap annular flow field has been derived by means of perturbation method. The effects of stator and rotor wall roughness on the dynamic coefficients of the eccentric rotor in large gap annular flow have been investigated with numerical method. It has been found that the numerical results of the dynamic coefficients agree well with the existing analytical solutions and experimental results. The roughness of the rotor and/or stator wall has considerable effect on the dynamic coefficients of rotor in large gap annular flow.