Abstract: Perovskite thin films fabricated through the solution process exhibit a significant number of internal defects. These defects serve as nonradiative recombination centers, markedly reducing photoluminescence intensity. While light treatment offers a promising method for passivating such intrinsic defects, the effectiveness of passivation is highly dependent on the duration of illumination. A photoluminescence detection system has been developed for the in-situ measurement of photoluminescence in perovskite films during light treatment. In this system, the excitation light source for photoluminescence also functions as the light treatment source. Utilizing this setup, the impact of varying light treatment durations on the photoluminescence of perovskite films is investigated. The findings indicate that as the light treatment duration increases, the peak intensity of photoluminescence progressively rises and eventually reaches a plateau. An optimal light treatment duration is identified. Under the optimal light treatment condition, the photoluminescence intensity of the perovskite films is amplified by more than fivefold. The above research result indicates that a photoluminescence online monitoring module can be introduced into perovskite film light treatment equipment to monitor and optimize the improvement effect of light treatment on the quality of perovskite films.