PEGASIS protocol is the classic chain routing protocol, its network is formed into a chain by greedy algorithm, the cluster head is generated by random selection, which is easy to lead to uneven energy consumption of the nodes and large network latency. Aiming at these problems, an improved PEGASIS routing protocol for wireless sensor networks is proposed. By calculating the optimal number of clusters, the nodes are divided into several original clusters, and the ant colony optimization algorithm is used to form chains within the clusters. During network operation, dynamic time intervals are taken to update the chains based on the energy of the nodes to prevent premature death of nodes. The results show that the proposed protocol can prolong the lifetime of the network compared with the PEGASIS and PEGASIS-REDP.