Abstract: The present disclosure discloses a twill optical film capable of realizing a 3D effect of a naked eye of a display screen and a preparation method thereof. The preparation method of the twill optical film includes the steps of: step 1: coating a grating coating with a high refractive index on one side of a transparent base film using a micro-nano imprint technique, and curing same by ultraviolet to form a uniformly arranged columnar lens array; and obtaining a twill grating layer; step 2: coating a filling coating with a low refractive index on the twill grating layer and curing same by ultraviolet; placing same in an oven in an atmosphere with a relative humidity of 95-98% controlled by a saturated solution of ammonium dihydrogen phosphate; setting the temperature to 100-120° C., and thermally cross-linking same for 3-4 hours; and obtaining a twill optical film.