The present invention provides a method for preparing a micro-cavity array surface with an inclined smooth bottom surface based on an air molding method. The method includes: preparing a micro-cavity array surface; preparing an auxiliary microstructure polymer template, and performing plasma treatment on the auxiliary microstructure polymer template; uniformly spreading a layer of a liquid polymer film to be formed on the auxiliary microstructure polymer template subjected to the plasma treatment; placing a gap bead in an empty position on the micro-cavity array surface; placing the auxiliary microstructure polymer template spread with the liquid polymer film on the gap bead on the micro-cavity array surface, maintaining this state, and feeding the auxiliary microstructure polymer template into a vacuum drying oven; and heating and solidifying the liquid polymer film, and separating the micro-cavity array surface to obtain the micro-cavity array surface with the inclined smooth bottom surface.