The XML stream filtering is gaining widespread attention from the research community in recent years. There have been many efforts to improve the XML system performance by utilizing XML schema information. In this paper, we design and implement an XML stream filtering system, SFilter, which uses DTD information for improving the performance. We propose the simplification and optimization algorithm of the XPath queries by using DTD information, and then we present the novel filtering algorithm for the resulting transformed XPath queries. The experimental result shows that our system filters the XML streams efficiently.