Storage schema is a key research field in the community of XML data management. About the performance, expressions of the underlying storage have very important effects on the top queries and optimizations. Therefore, effectively building the storage schema of the XML is the primary problem. This paper proposed an edge-mapping XML document storage schema, which effectively maps the XML database onto relational database. In this schema: firstly, the XML document tree was structured according to the type of the document node. Secondly, a union-table was used to store the value of nodes, and we only recorded the path of the element nodes by the mean of the node sequence number combined with the path. Finally, based on this storage schema, we implemented the database operations on the new database model. Experiments showed that the model can speed up the query procedures and can spare more memory space.