Wireless Sensor Networks (WSNs) are an important for monitoring distributed remote environments. As one of the key technologies involved in WSNs, nodes fault detection is indispensable in most WSN applications. It is well known that the distributed fault detection scheme checks out the failed nodes by exchanging data and mutually testing among neighbor nodes in this network but the fault detection accuracy of a scheme would decrease rapidly when the number of neighbor nodes to be diagnosed is small and the node’s failure ratio is high an improved scheme is proposed by defining new detection criteria.