With the development of information retrieval technology and database theory, how to achieve information retrieval technology in relational databases to obtain useful information, and the normal user can also be performed in relation database query with keywords, as recent research hot spot. Relation Database query system based on keyword, with which the user don’t need to know the database schema and structured query language, just inputting a few keywords. The article based on a prototype relational database-ER diagram, grouping entity according to different meaning. Following the keywords belonging to relation table, we can ensure the set of query entity, and dividing the range of query, to improve the efficiency of query. This paper presents a new algorithm to improve system precision. Finally, through experiments on the E-RKS system verifies verification.