XML is very attractive for platform independent information exchange, and hence XML streams are becoming very common. In this paper, we discuss and propose an efficient approach to deal with XML streams. Instead of using finite-state automata, we use parse trees in our approach. Moreover, we try to release results to users as soon as possible, through early predicate evaluation. The implemented system accepts for-let-where XQuery queries. After conducting experiments to examine our approach for processing XML streams, we got good results which demonstrate the efficiency, applicability and effectiveness of our approach.