The study evaluated co-digestion of spent mushroom compost (SMC) with striped fishpond sludge (FPS) in various C/N ratios in order to assess optimum proportion. Codigestion of SMC and FPS performed better in methane potential than the sole digestion of FPS. As the C/N ratio increased, both biogas and methane potential increased and then
declined. Higher C/N ratio set up, better co-digestion performance with stable pH and greater buffering capacity improved bio-methanation and greater biogas production. A C/N ratio of 40/1 showed optimum biogas yield and methane yield (283.25 L.kg VS_added^-1 and 142.85 L.kg VS_added^-1) in a batch testing with hydraulic residence time of 60 days. In the batch experiment, methane concentration was recorded higher than 50% after two weeks of fermentation. For the semi-continuous experiment, the average biogas production rate was 102.69 L.kg VSadded-1 and the methane content greater was more than 50% after three weeks of testing. This result suggested that better performance of anaerobic co-digestion of SMC and FPS can be fulfilled by optimizing C/N ratio.