A method for substance identification and an apparatus thereof are disclosed. The method comprises comprising steps of: transmitting an object under inspection using high-energy rays and low-energy rays, so as to obtain a high-energy transmission image and a low-energy transmission image for the object, wherein a value of each pixel in the high-energy image indicates a high-energy transparency of the high-energy rays with respect to corresponding parts of the object, and a value of each pixel in the low-energy image indicates a low-energy transparency of the low-energy rays with respect to corresponding parts of the object; calculating a value of a first function for the high-energy transparency and a value of a second function for the high-energy transparency and the low-energy transparency, for each pixel; and classifying locations determined by the value of the first function and the value of the second function using a pre-created classification curve, so as to identify the type of the substance of a part of the object corresponding to each pixel. With the present invention, it is possible to not only obtain a transmission image of the object, but also obtain material information in the object.