In order to further verify whether there still exists defect in the design of wireless transaction protocol (WTP), WTP is formally analyzed by model checking. First, WTP is modeled by finite state automatas (FSAs). Then the security property of the protocol is specified by computation tree logic (CTL). Finally, the obtained model and security property are verified by symbolic model verifier (SMV). The result shows that there exists a security flaw - deadlock in WTP.