Abstract: The intelligent fault diagnosis should be based on a perfect sample database，which must contain enough sampled data obtained from different working conditions. But many faults，especially in some special conditions，cannot be gained by experiments or practical samplings，so they need to be accumulated through numerical simulations. Based on the basic fluid principle，the influence of blade damage on the flow field and moments fluctuation of fully appendage underwater vehicle under uniform flow is obtained by solving the three-dimensional unsteady Reynolds average N-S equations and turbulent flow closed equations. The coupling mechanism between blade damage characteristics，propulsion efficiency and hull dynamics characteristics is concluded by field strength analysis. The results show that the pressure plays a leading role on total moment compared with the viscous force. The fluctuation of pressure moment can be divided into a large-amplitude low-frequency oscillation and a small-amplitude high-frequency oscillation. The frequency for the former oscillation mostly depends on the detached vortex frequency，and the frequency for the high frequency oscillation is consistent with the propeller rotation frequency. For the large amplitude oscillation of pressure moment coefficient，the thrust eccentric position of blade determines the offset of the balance line relative to the zero position. The phase difference between pitch and yaw moments reflects the symmetry of blade，and the smaller the phase difference is，the stronger the symmetry of blade will be. The blade damage types are predicted from the change of viscosity moment.

Key words: fullappendagesubmarine, propeller, bladedamage, faultidentification, couplingmechanism