In clustering algorithm of wireless sensor networks, to solve the problem of excessive energy consumption in the cluster heads, an residual energy and node degree synthesized clustering algorithm named ENCA (energy and node degree synthesized clustering algorithm) is proposed in this paper. In cluster heads election phase of every round, it considers the residual energy and the average energy of all the nodes in each cluster, an optimal cluster head is elected in each cluster according to node degree. In algorithm running phase the connection of the network is guaranteed, in the mean time, it is avoided to select the node with low energy as cluster head. Simulation results show that, in comparison with LEACH and ACE, the node energy consumption is balanced and the network lifetime is efficiently prolonged in ENCA algorithm.