Cloud provides plenty of storage that makes enterprises to move their precious information/documents to the cloud. Since the user moves their valued data to the cloud, security is a major concern between storage service provider and user. To ascertain the security, the cryptography plays vital role in the searchable encryption based document. In this paper, Dynamic multi keyword based search Algorithm is proposed that contain modified fully homomophic encryption and prims Algorithm. Based on keyword frequency present in the document, keywords are sorted and built searchable index for keyword and files. The dynamic tree is constructed using prim‘s algorithm based on keyword and file. The encrypted files in the tree are indexed to keywords using two way Hash table for efficient search and retrival of documents. The files are encrypted using modified ring based fully homomorphic encryption. The experimental result shows that proposed work provides 80 and 86% encryption and decryption throughput and take less indexing time to index the files than existing RC4+.