Abstract: In cloud storage, to protect the data security and privacy of data owners, data encryption is used to provide on-demand data services. Searchable encryption technology is the key method to solve encrypted data access. However, the multi-keywords in search do not distinguish and ignore the correlation between indexes, which will cause long search time and low accuracy. To this end, this paper proposes a multi-keyword searchable encryption algorithm based on semantic extension. Firstly, the dependency syntax is based on to distinguish the importance of multiple keywords for semantic expansion, and generate multiple keyword trapdoors. Secondly, the condensed hierarchical clustering and the keyword balanced binary tree are based on, and the index tree structure of index relevance is constructed. Finally, the pruning parameter and the correlation score threshold are introduced to prune the index tree, and the index-independent subtree is filtered out in the index tree. Theoretical and experimental analysis based on real data sets shows that the proposed algorithm can resist scale analysis attacks and improve search time efficiency and search accuracy.