Abstract: The light which goes through a doubledeck rectangle phase grating with different incidence angles can produce different numbers of beams. Based on the phenomenon, the beam which has high efficiency and uniform distributed light intensity can be obtained by changing and optimizing the grating′s incidence angle. The method of making a new type of splitter by the realtime variational beam feature of the doubledeck rectangle phase grating was investigated theoretically. Two, three or four beams produced by the method were analyzed respectively. Through the simulation with a computer, the optimizing parameters of incidence angle were theoretically derived and the result was discussed. Theoretical analysis shows that the splitter with high diffraction efficiency and uniform distributed light intensity can be designed by incidence angle optimization. The study provides a theoretical basis for making practical and cheap splitting device.