Disclosed are an energy spectrum modulation apparatus, a material discrimination method and a device thereof, as well as an image processing method are disclosed, which can discriminate the material in large- and medium-sized objects such as cargo containers, air cargo containers, etc. by using X-rays having different energy levels. The energy spectrum modulation apparatus comprises a first energy spectrum modulation part for modulating a first ray having a first energy spectrum, and a second energy spectrum modulation part coupled to the first energy spectrum modulation part and for modulating a second ray having a second energy spectrum different from the first energy spectrum. The present invention can be used in the non-opening inspection for large-sized container cargo at places such as Customs, ports and airports.