To improve the adaptability and stability of Dijkstra algorithm for solving routing problem of service composition, a method to solve routing problem of service composition based on an improved ant colony algorithm is proposed. Firstly, based on the traditional ant colony algorithm, the constraints of it are improved. Secondly, a problem solving model for improved ant colony algorithm is established, and the solving process is presented. Finally, simulation experiment will show that improved ant colony algorithm is more applicable in solving routing problem of service composition.