Abstract: In order to study the potential of methane production from co-degradation of rice straw and different rank coals,the effect of coal rank and the mass ratio of rice straw to coal on methane yield was determined.The interrelation between coal and rice straw under biodegradation was analyzed by scanning electron microscopy.The results showed that rice straw could significantly promote the conversion of coal to biogenic methane in coal seam.Under the condition of mass ratio 0.3∶1 of rice straw and coal,the maximum methane yields of co-degradation of high-rank coal,medium-rank coal,low-rank coal and rice straw were 643.25、627.90、208.46 μmol/g,respectively,which were 1 268.08%,1 644.16%,1 633.33% more than that produced from only coal as substrate,and 556.12%,540.17%,112.24% more than that produced from only rice straw as substrate.The results of orthogonal experiment showed that the lower the coal rank,the greater the proportion of straw added to produce the most methane.The best quality ratios of straw to high-rank coal,mid-rank coal and low-rank coal were 0.6∶1,1∶1 and 1.5∶1,respectively.The SEM results showed that the structure of rice straw and coal were damaged greater after co-degradation,and there was a synergistic effect between rice straw and coal.These results provide that the potential of co-degradation of methane from rice straw and coal is great,which provides an effective way to further improve the biological methane production in coal seam and the efficient utilization of rice straw resources.