Bio-methane is an attractive energy source which can be produced by utilization of waste sources through anaerobic digestion process. However, low methane content of biogas hinders its effective applications. In this study, photosynthesis reaction was used concurrent with anaerobic digestion as an effective controlling mechanism for biogas up-grading and enhancement of its methane content. For this purpose, photosynthesis assisted anaerobic digestion of cattle manure leachate was conducted at light intensities of 2700, 5900 and 9600 Lux in batch bioreactors. The effect of illumination intensity on COD removal, biogas composition and yield was investigated. Moreover, the concentrations of phosphate and nitrate as major intermediates in anaerobic digestion and photosynthesis processes were monitored. Results showed that COD removals of 51, 53 and 54% and specific methane yields of 0.058, 0.036 and 0.024 L CH4/g CODremoved were obtained for light intensities of 2700, 5900 and 9600 Lux, respectively. At light intensity of 2700 Lux, the highest methane content of almost 90% and nitrate removal of 48% were achieved. At this condition, the concentration of methane in biogas was high enough to be considered as a prospective energy carrier.