A method of image edge detection based on artificial fish swarm algorithm(AFSA)with chaos differential evolution algorithm(CDEA) is proposed in this paper. The method gets gradient matrix of grayscale image by first-order derivative, and search the maximum of image gradient with artificial fish. The detecting image edge could be achieved rapidly and accurately. The ability of search can be improved with adjustment factor in CDEA. It dynamically adjusts the vision, makes the fish jump out of the local extreme. The simulation shows that the proposed algorithm is feasible and effective.