The study was conducted in batch anaerobic digesters of 21L in lab conditions for 60 days. The mixing ratios of rice straw and pig manure were 100% of pig manure, 20% of straw + 80% of pig manure, 40% of straw + 60% of pig manure, 50% of straw + 50% of pig manure, 60% of straw + 40% of pig manure, 80% of straw + 20% of pig manure, and 100% of straw. These experiments were arranged randomly in batch anaerobic reactors with volume of 21 liters; each mixing ratio was repeated five times. The results showed that rice straw have a high potencial of enhancing biogas production due to mixing with pig manure. Mixing ratios of rice straw and pig manure at 50% and 60% had highest gas yield (846,6 and 841,8 L/kg VS _degraded), which were not different from other mixing ratios except in the ratios of 100% of straw and 100% of pig manure (P<0.05)