As various users and applications require the distribution and sharing of information in XML documents, the need for an efficient secure access of XML data in a ubiquitous data stream environment has become very important. In this paper, we propose an efficient secure XML query processing method to solve the two problems by using role-based prime number labeling and XML fragmentation. A medical records XML document has the characteristic of an infinite addition in width rather than in depth because of the increment of patients. But a role-based prime number labeling method can fully manage the size of documents that increases to infinity and can minimize the maintenance cost caused by dynamic changes. Experimental evaluation clearly demonstrates that our approach is efficient and secure.