The floating display is a very promising technology which can display images in the air, giving the viewers immersive and immediate experience. A floating 3D display system based on the integral imaging is proposed, which consists of an integral imaging 3D display, a semi-translucent semi-retroreflective mirror and a retro-reflective film. The working principle of the integral imaging 3D display and the floating display principle of retro-reflective film are analyzed. Therefore, combining the integral imaging 3D display technology with the floating display technology based on a retro-reflective film, the light rays from the integral imaging 3D display will reach the retro-reflective film through the reflection of the semi-transparent and semi-retroreflective mirror, and the retro-reflective film reflects the light at the angle of incidence and reconstructs the 3D image again, which solves the problem of depth inversion of the integral imaging 3D image while realizing the floating 3D image display. The system provides a new theoretical basis for floating 3D displays and a new method for solving the depth inversion of integral imaging 3D images.