Aiming at the weak information dispersion ability and low security performance of existing medical image encryption algorithms, a DICOM medical image encryption algorithm based on double chaotic structure, DNA dynamic coding and block diffusion is proposed. A new three-dimensional hyperchaotic system is designed and a hyperchaotic Chen system is introduced to form a double chaotic iterative generation system to avoid the risk of a single system being cracked by reverse deconstruction analysis. Optimize the DNA encoding mechanism and combine it with the chaotic sequence to realize the DNA encoding of dynamic rules and improve the anti-decoding ability of the algorithm. In addition, in the diffusion stage, the matrix information is divided into blocks and the pixel information is processed bit by bit by a Zigzag-like loop traversal method. Through various security analysis experiments, it is proved that the ciphertext image has good encryption performance and high security in terms of statistical characteristics, information entropy, key sensitivity and space size, and has a certain level of security in the field of medical image encryption. prospect.