This study aimed to make use of paddy straw and limit the gas emission from the practice of straw in situ burning. Lab-scale 21 L batch anaerobic digesters were set up to ferment paddy straw in 60 continuous days. Straw was cut in different sizes and pre-treated with digester’s effluent for 5 days. The temperature, pH, and redox recorded daily in most of the treatments were in good conditions for methanogen. The gas yield from the treatments of rice straw 0.2 cm was 760 L/kg ODM_fermented, 0.5 cm - 756 L/kg ODM_fermented, and 1.0 cm - 764 L/kg ODM_fermented which was higher than the treatments of 0.05 cm - 677 L/kg ODM_fermented and original size - 698 L/kg ODM_fermented. The CH₄ content in all treatments got more than 45% after three weeks. The results confirm that the anaerobic practice could produce biogas from paddy straw and this can help reduce the local practice of burning straw on field.