To enhance the security of encryption algorithms and solve periodicity problem with Sine mapping and ICMIC(iterative chaotic map with infinite collapses) mapping, a multi-stage encryption algorithm combining 2D mapping with Z-shaped spiral scrambling and DNA coding was proposed. Firstly, a new chaotic map SUIM(Sine union ICMIC mapping) was obtained by combining Sine map and ICMIC map. The encryption algorithm mainly used SHA-512 to generate key from the plaintext image, used the proposed Z-shaped spiral transform and bidirectional Zigzag transform to scramble plaintext images, and improved boundary pixel replacement to enhance image resilience. Subsequently, pixel random diffusion and DNA level secondary diffusion processing were performed. Results show that the proposed encryption algorithm has higher information entropy, better resistance to differential attacks, lower correlation between adjacent pixels, and further guarantees the security and privacy of image data.