In order to reduce the energy consumption caused by node address and send message in wireless sensor network, detection and reuse redundant nodes for media access control (MAC) address assignment algorithm in wireless sensor networks (WSN) was proposed. In this algorithm, the MAC address was divided into cluster address and inner-cluster address by using address multiplexing ways. Detecting redundant nodes and making it dormant before inner-cluster address assignment. In this way, the number of nodes involved in assigning address and the energy consumption of sending message were reduced. Then, the inner-cluster address is assigned with different lengths according to remaining energy and the number of neighbors of a node. When the network updates address, redundant nodes can be used to replace of the death node. Simulation results show that the proposed algorithm can efficiently decrease the average address length and communications volume, and extend the lifetime of the network.