With the development of cloud computing, the sensitive information of outsourced data is at risk of unauthorized accesses. To protect data privacy, the sensitive data should be encrypted by the data owner before outsourcing, which makes the traditional and efficient plaintext keyword search technique useless. Hence, it is an especially important thing to explore secure encrypted cloud data search service. In this paper, we propose a practically efficient and flexible searchable encrypted scheme which supports multi-keyword ranked search. To support multi-keyword search and result relevance ranking, we adopt Vector Space Model (VSM) to build the searchable index to achieve accurate search result. To improve search efficiency, we design a tree-based index structure. We propose a secure search scheme to meet the privacy requirements in the threat model. Finally, experiments on real-world dataset show that our scheme is efficient.