Abstract: The rapidly image separate (RIS) method, a new kind of technique is developed, which allows us to separate the images of different component by processing the different images of an object produced by microfocus X ray beams of different energy. Its application to a acrylic aluminum material has been proved through the experiment. The conditions for the realizing of the RIS method with the microfocus X ray generator, including the voltage and amperage of the X ray tube, the size of acrylic and aluminum material, the cause of error, are discussed. An idea to improve on the RIS method and the mathematical model of correcting error is given, and the vista of this method is also provided.