Abstract: Considering the problem of multi-keyword fuzzy matching and user fairness in one-to-many data ciphertext sharing, a multi-keyword fuzzy search encryption scheme based on blockchain is proposed. An R-HashMap index structure is proposed. The secure index is constructed by using pairs coding function and position sensitive hash function, and the K-nearest neighbor algorithm is used to encrypt the index. The similarity between the query keyword vector and the index node is calculated by Euclidian distance measure, and the multi-keyword fuzzy ciphertext search is realized. In addition to eliminating the pre-defined dictionary and reducing the storage overhead, this scheme also realizes the update of the security index without increasing the search complexity. In addition, the combination of Ethereum blockchain technology and searchable encryption scheme avoids data tampering by malicious servers, and the use of smart contracts as trusted third parties for retrieval work can not only prevent keyword guessing attacks within cloud servers, but also solve the problem of incorrect retrieval results. Through security proof analysis, the proposed scheme not only satisfies the semantic security of adaptive keyword selection, but also can protect user privacy and data security. The experimental comparison between this program and other schemes proves that the program has better efficiency in terms of time and cost while ensuring accuracy.