In order to improve the robustness of digital image watermarking, a digital image watermarking algorithm is proposed based on discrete cosine transform and Hamming code. Firstly, Arnold transform and Hamming code are used to scrambling encryption and encoding of the binary watermarking image. Then, the carrier image is divided to 8×8 blocks, and each sub-block is carried on two-dimensional discrete cosine transform respectively. Finally, the encrypted and encoded watermarking is embedded into the middle frequency coefficients of the two-dimensional discrete cosine transform, the embedding strength is adaptively determined according to the characteristics of the carrier image. The experimental results show that the security and the imperceptibility of the watermarking are very good, not only it can effectively resist the attack of noise, resampling, filtering, compression, rotation, shearing and so on, but has good robustness against the many kinds of combined attack as well, and implements adaptive embedding and blind extracting of watermarking.