The photosensitized reaction of 8-Hydroxyquinoline have been studied in the alkaline medium in the visible light using methylene blue (MB) as photosensitizer. The rate of the reaction have been calculated. The effect of the parameters like pH, concentration of the sensitizer, concentration of the substrate, and intensity of the light on the rate of the photosensitized reaction has been studied. The reaction have been studied in anaerobic condition to observe the effect of the oxygen. Methanol shows free radical scavenging effect. The quantum efficiency of the photosensitized reaction have been calculated. The scheme of the reaction mechanism is suggested. The singlet state of the oxygen (1O2) participates in the photoreaction and photooxidation product is formed by oxidation of the substrate. The reaction have been studied using UV-visible spectroscopy and product analyzed with Mass-Spectrometry.