The invention provides a dual energy detection method and a dual energy detection device. The dual energy detection device comprises an X ray source, a scintillation detector, a Cherenkov detector, and a processor. The X ray source is used to emit X ray beams to an detected object. The scintillation detector works in an integral mode, and is used for receiving the X ray beams passing through the detected object to generate a first electric signal. The Cherenkov detector is located behind the scintillation detector, works in a counting mode, and is used for receiving the X ray beams passing through the detected object to generate a second electric signal. The processor is used for outputting the image, the volume and the material information of the detected object according to the first electric signal and the second electric signal. The dual energy detection method can obtain a clearer image of the detected object, which contains more information.