In this paper, a set of dimension parameters of the sub-wavelength structural anti-reflection film are designed to improve the photoelectric conversion efficiency of flexible substrate solar cell and reduce the surface reflection losses. The designed parameters are simulated in TracePro optical simulation software. The simulation results show that the flux enhancement effect is optimum when the Nano-column height is 72 nm, the duty ratio is 0.5 and the grating period at 300-440 nm for the sub-wavelength structural film. Using Nano-imprinting technology, a polyimide membrane anti-reflection is fabricated based on the template of a vesicular structural anodic aluminum oxide (AAO). The influence of the technological parameters, which is of the fabricated AAO template and its Nano-imprinting technology, on the polyimide (PI) transmittance of the films is tested by scanning electron microscope and ultraviolet-visible light detector. In experiments, we fabricate the AAO template in 0.3 mol/L oxalic acid solution consecutively reacting for 1 h in 70 V constant voltage mode. The PI film is obtained with the insulation being 10 min at 280 ℃ and 800 kg pressure. The test results show that when the transmission spectrum is from 440 nm to 1 000 nm in air mass 1.5 (AM1.5) atmosphere, the transmittance of the film is increased by 2%~5% than the primitive PI film.