The invention provides a hydrophilic film allowing liquids to directionally and rapidly diffuse in single direction. The hydrophilic film comprises a substrate and a hydrophilic coating, wherein the substrate has a parallel concave-convex structure, and the hydrophilic coating include a silicon dioxide coating. The invention also relates to a preparation method of the hydrophilic film. The method comprises the following steps: preparing a silicon dioxide water-based dispersion liquid, wherein the average particle size of silicon dioxide is 1-60nm and the concentration of silicon dioxide ranges from 0.05% to 15% by weight; applying the silicon dioxide water-based dispersion liquid onto the substrate with the parallel concave-convex structure; drying the substrate onto which the silicon dioxide water-based dispersion liquid is applied.