Disclosed is a dual-link wireless ad hoc network and a security defense method in an emergency scene, aiming at comprehensively improving its security defense capability. The method comprises: sending, by a source node, the secret key and other messages which are not security defense messages through the second link; detecting, by a destination node, abnormal messages from the acquired valid messages after matching with abnormal message feature library, filtering the abnormal messages out, and quickly broadcasting the features of new abnormal messages through the first link; checking, by a new node to be added to the network, the identity and hardware state, authorizing the new node without abnormality, and broadcasting the authorization result information through the first link; adding, by other nodes receiving the security defense messages, the features of the new abnormal messages to their own abnormal message feature library, and allowing the entry of the new node.