Abstract: A wormhole attack destroys routing operations, affects the node positioning, and poses great threats to the security of the entire wireless sensor network (WSN). Aiming at resolving this issue, the grid based wormhole attack defense strategy was presented. Through additional grid properties, information was exchanged with nodes in specific grids to detect wormhole attacks, including attacks from special wormholes with the forgery and tampering ability in a network, thus greatly reducing damages brought by wormhole attacks. The simulated experiment proves that malicious nodes can be effectively detected in an attacked network if this strategy is used.