This document proposes a secure multi-keyword ranked search scheme over encrypted cloud data that allows for dynamic operations like document deletion and insertion. It constructs a special tree-based index structure and uses a "Greedy Depth-first Search" algorithm to provide efficient search. The vector space model and TF-IDF model are used to construct indexes and queries. The scheme aims to achieve sub-linear search time while supporting dynamic document operations and ranking search results based on relevance.