Abstract: Based on the comprehensive consideration of the robustness and embedding capacity of the reversible watermarking algorithm, A cryptographic domain reversible watermarking algorithm based on ciphertext domain extension is proposed. This algorithm not only ensures high robustness, but also makes the embedding capacity as high as 8.0625dB. Firstly, the two-dimensional carrier image and the two-dimensional watermark image are encrypted based on IWT and DNA bidirectional encoding. Then, the encrypted watermark is embedded into the encrypted carrier image based on the ciphertext domain extension, and finally, the two-dimensional carrier image is converted into a watermarked image. Three-dimensional image, the algorithm is completed.The SSIM evaluation index is used to analyze the restoration quality of the image. The SSIM value is 1 and the algorithm is completely reversible. The embedding capacity of the algorithm is 8.0625dB, which is much larger than other literatures. The robustness analysis shows that the algorithm is better. The algorithm achieves the complete reversibility of the watermark information in the ciphertext domain and the lossless recovery of the original image under the premise of ensuring the security of the original carrier content.