Diffractive optical element (DOE) has unique dispersion characteristics and flexible design freedom. The cascaded DOE was applied in the concentrator system of solar cell to achieve focusing, shaping and spectrum separation function and the design methods and algorithms were presented. Seven regular shaped and completely separated spots were observed on the target surface when simulating with the mixed seven-wavelength light. It is proved that the cascaded DOE structure can effectively enhance the efficiency of solar energy utilization.