Abstract: To improve energy efficiency in wireless sensor network(WSN), an energy efficient routing algorithm was proposed on the basis of the self-adaptability and dynamic optimization of ant colony system(ACS) and the self-organized property of WSN. Residual energy was considered to compute local heuristic factor to optimize the path probability selection and balance energy consumption among nodes. Quality of each path was introduced into the global pheromone update, which was evaluated by using the path length, the average pheromone of the path, and the average residual energy of nodes in the path. Multiple dynamic optimized paths were explored and maintained between source nodes and Sink to improve the robustness of transmission. Simulation results indicated that the proposed algorithm can decrease delay, improve energy efficiency and prolong the lifetime of WSN.