It’s important to measure the horizontal distribution of the 2D velocity field for model verification and scheme selection at model test in the tidal estuary. Digital particle image velocimetry (DPIV) has become an accepted technique for the measurement of two- and three component planar velocities in a wide variety of fluid flows, which has advantages of high speed and nil interference. However, sometimes DPIV images are overexposure, uneven distribution of the gray values, and obscurity on the edges of the particles, which will affect the accuracy of flow data by inversion. Wavelet transform has good characteristics in time-frequency localization, and it has been widely used for image preprocessing, image compression, image restoration, image feature extraction and pattern recognition. A wavelet-based multi-resolution technique was applied to analyze the 2D measurement results of a DPIV system in this paper. In the different stages: boundary treatment, noise reduction, identification and elimination of the error vector, which are applicable to the processing of the DPIV information for getting the velocity vectors with higher resolution and precision through the continuous wavelet transform of velocity data.