The invention provides a security inspection system for inspecting persons, characterized in that it comprises: a passageway which provides an inspection space isolated or partially isolated from an ambient environment, in which at least one sub-passageway allowing persons to be inspected to pass is provided in the inspection space, and each of the sub-passageways is provided with at least one millimeter wave imaging device for millimeter wave imaging of persons being inspected; and an ion mobility spectrometer for ionizing particles of substance or gases that are released or volatilized from the inspected persons into the air in the passageway and then measuring a mobility rate thereof under the action of the electric field to effect identification of substances. At least one radioactive substance inspection device may also be provided in the passageway to detect whether the person being inspected carries radioactive substances.