Abstract: Wireless Sensor Network(WSN) has broad application prospects. Routing protocols which are the key technology of WSN have become one of the focuses of research. For the problem of “data-unreachable” about the SPIN(Sensor Protocol for Information via Negotiation) routing protocol, this paper describes the problem’s cause of formation. and resolve the problem of “data-unreachable” through define a new data information—CA（Compulsory Advice）and design a timer. Using these methods, the paper avoid the problem of “data-unreachable”.