Abstract: In this paper the Db3 wavelet transform is applied to study instantaneous velocity of sedimentladen flow measured by the MicroADV, and according to the characterize of local property of the wavelet in time frequency, the high frequency noise is easily removed.The de-noised velocity is further analyzed as the higher frequency and the lower frequency part, the lower scale represents the regularity of velocity fluctuation on the whole and relates to coherence of turbulent, and the higher scale represents the fine structure of velocity fluctuation, which relates to the isotropic characteristic of turbulence.