A method for manufacturing an array substrate, a film-etching monitoring and a film-etching monitoring device. The monitoring method comprises: monitoring and recording the transmittance reference value of a film after a film pattern is formed; and monitoring the transmittance present value of the film in real time in the process of etching an overcoating layer to form a through hole after the overcoating layer is formed on the film pattern, and monitoring the etching degree of the film by determining the variation between the transmittance present value and the transmittance reference value. The device comprises a plurality of light sources (3) and a plurality of light-sensitive probes (4) disposed in the chamber. The light sources (3) are configured to irradiate the film on a substrate; and the light-sensitive probes (4) are configured to sense the transmittance of the film.