The invention relates to an ultra-low-dose X-ray human body security inspection system with double exchange platforms, the system comprises an X-ray source, a collimation part, an inspection channel, an X-ray detector, an image acquisition and processing device, a control device and an operation console, wherein the inspection channel comprises an inlet, an outlet and a mobile inspection platform, the mobile inspection platform is a dual-circulation platform and comprises a first platform, a second platform, two upper tracks, two lower tracks, a platform driving mechanism, a platform lifting link mechanism and a base, the first platform and the second platform are respectively movably mounted on the upper tracks and the lower tracks and move along the reverse directions of the upper tracks and the lower tracks under the drive of the platform driving mechanism arranged on the outer side, and the upper and the lower positions of the first platform and the second platform on the lower tracks and the upper tracks are exchanged through the platform lifting link mechanism after running in place at each time. The ultra-low-dose X-ray human body security inspection system can double improve the inspection capacity and the customs clearance efficiency, have smooth running, good linearity and uniform movement speed and greatly improve the X-ray inspection imaging quality.