Mini LED backlight display products use optical diffusion plates and composite films to improve brightness and uniformity. The test results of this paper show that the brightness gain of composite films ranges from 1.5 to 2 times, with the order of brightness gain being POP>DPP>MOP>DOP. This is due to the correction effect of different composite films on the beam solid angle. At the same time, the composite film raised the backlight color coordinates, with the change in the diffusion plate+DPP color coordinates being Δx of 0.01 and Δy of 0.018 7. Analysis shows that the significant loss of short wavelength blue light radiation energy is caused by Mie scattering of diffusing particles. The blue light reflected back from the multi-layer optical microstructure of the composite film to the quantum film will generate multiple photoexcitation phenomena, further increasing the amplification of the xy color coordinate values of the quantum dot model by the composite film. The color coordinate changes generated by the optical composite film are beneficial for adjusting the color temperature of the display product to a lower color temperature from the factory to ensure display brightness.