In this paper, a kind of composite diffractive optics array element, whose shape is approximately circular by containing some series of square units with different sizes, is designed to obtain a focal spot with flat top, steep edges and low sidelode intensity distribution. For an incident laser beam with circular shape, a large filling factor can be realized and light energy can be sufficiently used. Two dimensions are converted to one dimension to simplify the design and manufacturing. Hybrid algorithm based on hill-climbing and stimulated annealing is utilized for phase design. Simulated results show the validity of this kind of method.