The advantages and characteristics of detection of hidden explosives and radioactive materials by nuclear technologies are explained in this paper. The active neutron interrogation technology and their application to detection of explosives are introduced in detail. The non-neutron interrogation technology by gamma method, the commercialized industry neutron sources and gamma ray detectors and their advantages and disadvantages respectively in security application are summarized respectively. The security problem of two typical hidden explosives are discussed with 11 characteristics of a perfect detecting system of explosives. The current research progress in association with particle imaging and fast-pulse neutron system and the passive method to detection of radioactive materials are briefly described. Finally, the paper points out that for detection of hidden explosives and radioactive materials it is necessary to use different technologies for different scenes and targets or use combined technologies.