In order to balance the relationship between structure and performance in chaotic map and ensure the security of the encryption system,a block image encryption algorithm based on cosine-exponential chaotic map is proposed.Firstly,a new cosine-exponential chaotic map is constructed by modulating the cosine map with the introduction of the Tent seed map through the non-linear exponential term,and the SHA-256 function is used to generate the key associated with the plain-text,generating chaotic sequences with strong randomness to achieve one-time pad.Then,based on the Latin square and bit-level transformation,the double Latin square and extended bit algorithm are designed through two rounds of Latin square indexing and bit stitching,respectively,and combined with two-dimensional Josephus sequences,to scramble the inter-block pre-scrambled plain-text within blocks,achieving differential scrambling of different blocks.Finally,based on the Zig-Zag transform,the cross Zig-Zag transform method is designed using a circular imitation Zig-Zag transform,which diffuses the intermediate cipher-text with the chaotic sequence nonlinearly in both directions to achieve simultaneous change of pixel position and pixel value to complete the image encryption.The experimental results show that the algorithm has a large key space and can effectively resist typical attacks such as differential analysis and statistical analysis,and has a good encryption effect.