A secure Multi-Keyword ranked search scheme over cloud data is presented; it supports dynamic update operation like deletion and insertion. Greedy Depth first search algorithm is used to provide efficient multi keyword ranked search. The scheme aims to achieve sub linear search efficiency by exploring a special tree based index and an efficient search algorithm. A secure tree-based search scheme over the cloud data, It supports multi=keyword ranked search and dynamic operation on the document collection. The secure KNN algorithm is utilized to index and query vectors and ensure accurate relevance score calculation between index and query vectors. A searchable scheme that supports both the accurate multi-keyword ranked search and flexible dynamic operation on document collection