Abstract: The optimization of XML path expression, algorithms of querying and filtering were investigated. The fill path and the path shorten were used to optimize the path expression. The method that the path expression was optimized to improve query method’s speed was called path shorten strategy. The method that a simple path expression was used in full to replace the complexity of expression was called full path. In XML query processing, Xpath was used as a processing language to deal with XML query processing. The Xpath expressions and query processing were also studied. XPE-Tree was used to match in Xpath query processing, and twice path concatenation was used to achieve the query processing. The path XML expression was used in the filtration system to match the pattern and content. After the user information was input to system, filtering engine has been generated, then, the engine of the filter and the data stream were matched, the information that the user was interested was output, the filtration process has been completed