Abstract: This paper proposes a discrete wavelet transform (DWT)-based image watermarking algorithm using direct sequence code division multiple access (DS-CDMA) techniques, to resist cropping attack. The CDMA encoded watermark bits, concatenated by the synchronization code, are embedded into the selected DWT coefficients of the original image. During the blind recovery of the embedded data, the corresponding DWT coefficients of the cropped watermarked image are relocated by self-synchronizing efficiently, and then the correlation between the extracted watermark information and Gold sequence is analyzed. By exploiting the time-frequency localization characteristics of DWT, the computation load to search the synchronization code is reduced. The experiment results demonstrate that the generated watermark is robust to cropping, joint picture expert group (JPEG) compression, Gaussian noise and other common attacks.