The convenience of the network has brought the copyright crisis of some multimedia works. Therefore, a secure digital watermarking algorithm is urgently needed to realize the copyright maintenance of digital works. A blind digital watermarking algorithm using approximate Hadamard transform is presented in this paper. Since Hadamard transform has a certain energy aggregation effect, in this paper, the principle of energy concentration of Hadamard transform is explored, and the Hadamard transform is slightly treated, so that the multiple increase of large energy coefficient is realized. This modified approximate Hadamard transform is applied to the process of changing from spatial domain to transform domain in the embedding and extraction stage of our proposed watermarking algorithm. In this algorithm, the color image digital watermark is hided in the maximum energy coefficient of color host image in transform domain by using the idea of quantization. In the extraction stage, the watermark image can be extracted completely without the participation of any original information. In order to check on the feasibility of the algorithm, a large number of simulation experiments have been done. The results of simulation experiments show that the proposed algorithm has excellent effect in various performance index.