An optical functional film with triangular pyramidal texture is proposed to reduce the reflection loss of crystalline silicon cells in order to solve the problem where directly fabricating the light-trapping texture on the surface of crystalline silicon can increase of surface photogenerated carrier recombination in crystalline silicon cells. The models of the reflection and refraction loss of light on the surface of an optical functional film with triangular pyramidal texture are developed. Afterwards, the triangular pyramidal textured film is bonded to the smooth surface of crystalline silicon cells and the angle between the base and side of the triangular pyramid is optimized. According to the large-area fabricating process of the optical functional film with triangular pyramidal texture, the proper structural parameters of the textured film are obtained. The optical functional film with triangular pyramidal texture was fabricated by means of ultra-precision cutting, electroforming, and embossing processes. Moreover, the effect of the fabricating precision on the optical performance of the triangular pyramid textured film is analyzed. The experimental and analytical results indicate that, by using the triangular pyramid textured film, the reflection loss of the smooth surface crystalline silicon cells decreases from 22.3% to 7.2% and the photovoltaic conversion efficiency increases from 18.30% to 20.47%. Compared with conventional textured crystalline silicon cells, the photovoltaic conversion efficiency of smooth surface crystalline silicon cells with the proposed optical functional film increases by 0.99%. An optical functional film with a triangular pyramidal texture can effectively improve the absorbance and photovoltaic conversion efficiency of smooth surface crystalline silicon cells.