Abstract: XML is widely used as a standard of information exchange and representation. Queries on XML can retrieve a subset of XML data nodes satisfying certain constraints. Queries on large XML data are usually processed in two steps: 1. An index of XML nodes is created; 2. Queries are processed on that index without accessing XML data. XML index provides high efficiency for XML query processing. Particularly, F&B-index is the smallest index that supports twig query processing. However, few researches are proposed on how to efficiently create F&B-Index and how to process queries based on F&B-Index. Proposed in this paper is a new labeling scheme called prime sequence. This labeling scheme helps not only on creating an F&B-Index but also on efficient query processing. With prime sequence labeling, an F&B-index can be created by parsing the XML document only once with a SAX parser. Further, region encoding and CCPI on F&B-Index can be created during the creation of F&B-Index. Thus, TwigStack algorithm and related-path-join algorithm can be used to process queries on created F&B-Index. Also proposed is an efficient algorithm named division match over F&B-Index. The algorithm can efficiently judge relationship between two nodes based on a property of prime sequence labeling. Experiments show that prime sequence labeling provides high efficiency on creating F&B-Index and high efficiency on query processing on different datasets.