Abstract: In order to find out the promotion effect of different kinds of microbial pretreatment on the conversion of coal biogas,lignite was pretreated with three diff erent types of strains including streptomyces viridosporus,phanerochaete chrysosporium and pseudomonas,followed by measurement of gas production and compositio n after fermentation with coal seam methanogenic flora. The effects of different kinds of microbial pretreatment on total gas production and composition,as well as the C oal surface structure were investigated by biogas production effect detection, Gompertz equation simulation and scanning electron microscopy( SEM).The results show t hat compared to raw original lignite,the total methane production of lignite pretreated by streptomyces viridosporus,phanerochaete chrysosporium and pseudomonas inc reased by 36.86%, 165.28% and 69. 18%,respectively.The ftting data demonstrated that maximum specific methane production of streptomyces viridosporus,phanerocha ete chrysosporium and pseudomonas have increased 14.61%,154 49% and 96.10% ,respectively than that of raw original lignite.The effect of microbial pretreatment on coal-to-biogas conversion from strong to weak is followed by phanerochaete chrysosporitum,pseudononas and streptomyces viridosporus. The volume and adhesion cha racteristics of the different microorganisms have an important influence on the pretreatment effect. The smaller the volume of the strain,the better the pretreatment effec t,and the pretreatment promotes the pore-fissure and surface roughness of the coal to increase significantly,and providing convenient conditions for the later anaerobic fermentation bacteria to act on coal.