Hierarchy-based wireless sensor networks (WSNs) achieve excellent performance with reserving energy consumption and decreasing system delay. However, distinguished hierarchy-based research such as LEACH (Low-Energy Adaptive Clustering Hierarchy) does not consider a security issue for ensuring the protection of the network. Due to the peculiar character of LEACH such as round base operation and header centrality topology, adopting security in LEACH is a complicated task. In this paper, we present an authentication protocol for hierarchy-based WSNs to protect network from inside attackers. This protocol uses pre-distribution unique symmetric key with Authentication Management DataBase (AMDB) and live message to monitor the network to detect the entrance of compromise node using illegal keys.