Conformance testing is the procedure to verify whether protocol implementations conform to their specifications. In this paper, we propose a traversal probability based conformance testing method - TPBT, which can be used to test protocols specified as communicating finite state machines (CFSM) efficiently. In fact, TPBT is a random walk based adaptive method, which aims to traverse all transitions in component machines in steps as few as possible. We apply it to two example CFSM models, and the results show that it achieves better performance than other random walk based adaptive methods. Applying TPBT to the mobile IPv6 protocol, all component machines' transitions are traversed within about 600 steps, for which pre-generated test cases are tedious long and error-prone.