Terahertz science and technology has been rapidly developed in recent years, which make it a capable way to detect person-borne concealed threats. The advantages of terahertz imaging in standoff security inspecting application are introduced according to the characteristics of terahertz waves. A comparison is made between active and passive imaging, which are two main methods for terahertz personnel screening. Then the current status of terahertz imaging research in concealed objects detection is reviewed and commented. It is concluded that terahertz transceiver array, multi-band data fusion and active/passive composition would be the main techniques in future researches. This prediction is based on the analysis in the researches of main institutes in this field and recent programs in Europe. Some key technologies and main trends related to terahertz security inspection are pointed out.