Edge detection is playing an important part in image process,and is the foundation of successive work.There are various approaches to detect edges including the one based on ant colony algorithm.In view of that the traditional ant colony algorithm for the edge detection is usually time consuming,an improved ant colony algorithm was proposed.A new calculation method for heuristic information was presented by which,the movement of ants can be better guided.Experiments show that the proposed algorithm can extract the weak edges more quickly and accurately.