The invention discloses an active brightness enhancement film, a preparation method thereof and a method for analyzing the polarization of the active brightness enhancement film based on FDTD. The active brightness enhancement film comprises at least one layer of quantum dot doped polymer film and at least one layer of metal nanorod containing polymer film, wherein metal nanorods in the metal nanorod containing polymer film are uniform in orientation and are periodically arranged. The brightness enhancement film is unique in structure, efficient red and green fluorescence emitted by quantum dots can be obtained, and high-efficiency polarized light in a light source wave band can also be obtained. The active brightness enhancement film is economical in cost and excellent in performance, and the market monopoly formed by dual brightness enhancement films (DBEF) of 3M radicals is broken through. The invention also provides the method for analyzing the polarization of the active brightness enhancement film based on FDTD, and 3D-FDTD periodic boundary conditions are used, so that a great deal of computing time is reduced, and the method is an effective tool applicable for analyzing polarization behaviors of the nanorods.