A THz linear array scanning imaging system was built using a 0.3 THz radiation source and a linear array detector. The imaging system only needs 1 min to achieve an imaging measurement over a 100 mm×100 mm region at an imaging resolution of 1.5 mm. Using this imaging system, the defects embedded in polyethylene samples and water pipes as well as the scissors and knives concealed in envelopes are quickly and accurately identified. The research results demonstrate that the proposed imaging system can rapidly inspect various objects and is suitable for non-destructive testing and security inspection.