The present application relates to a dual energy detector and a radiation inspection system. The dual energy detector comprises: a detector module mount and a plurality of detector modules. The detector module includes a higher energy detector array and a lower energy detector array, which are juxtaposedly provided on said detector module mount to be independently irradiated. The present application may simplify the arrangement of the photodiodes and printed circuit boards to which the higher and lower energy detector arrays are connected, such that necessary thickness dimension of the detector module mount is reduced, thereby facilitating the installation and use of the dual energy detector of the present application. On the other hand, the radiation beam in the present application may be independently irradiated to the higher and lower energy detector arrays juxtaposed to each other, which reduces to certain extent the mutual restriction during selection of the higher and lower energy detector arrays.