Abstract: This paper gives a review about the effects of light on the activities of glyoclate oxidase in higher plants, It analyses the induction of glycolate oxidase by white light, light intensities, light qualities, etc., and discusses several hypotheses with which the former workers explained the action mechanism of light on this enzyme. On this basis, a new hypothesis is proposed, suggesting that the effect of light has two aspects. One of these is to make glycolic acid by setting photosyn-thetic process in motion. Then, being an effector, glycolic acid induces the biosynthesis of apoenzyme of glycolate oxidase. The other aspect of light effect is to acelerate the biosynthesis and changes of flavines and to raise the level of FMN in tissues. Then, FMN enters into combination with apoenzyme to make the holoenzyme of glycolate oxidase.