NOVELTY - For converting lignite (coal) (having particle size of less than 0.075 mm) into methane, microorganism obtained from sewage treatment plant activated sludge and biogas slurry flora, is used.    USE - For microbial conversion of lignite (coal) into methane (Claimed).    ADVANTAGE - The microorganism gradually domesticated and capable of the brown coal into methane by test detection, a small test synthesis efficiency of the coal powder can reach 11.8 ml/g, and large test (kg) coal synthesis gas rate is 0.19 ml/g; and improves production efficiency.    DETAILED DESCRIPTION - For converting lignite (coal) (having particle size of less than 0.075 mm) into methane, microorganism obtained from sewage treatment plant activated sludge and biogas slurry flora, is used. Where the method involves: a) active sludge flora inoculating and culturing step: adding to active sludge, glucose in water, ammonium chloride, potassium dihydrogen phosphate, and carrying out aeration treatment for 8 hours per day for 28 days; b) bacteria sludge acclimation step: allowing bacterial liquid broth obtained in step a), to sludge settling for 24 hours, removing the upper bacterial solution, adding 50 g pulverized coal having diameter of less than 0.075 mm and carrying out domestication and continuous acclimatizing for 28 days; c) to the anaerobic biogas source, inoculating brown coal powder having particle size of less than 0.075 mm for 15 days to obtain domesticated anaerobic bacteria source solution; d) coal processing and separating oil particles whose particle diameter is 0.075-0.1 mm, by adding pulverized coal broth obtained in step b) to obtain the bacteria liquid, supplementing with glucose every three days, after 15 days subjecting to continuous aeration and then subjecting coal to filtration and washing; and e) adding coal obtained in step d), and nutrient solution into a vessel, pumping nitrogen and oxygen with a peristaltic pump into the anaerobic bacteria source solution obtained in the step c), sealing, incubating at 35 degrees C to form methane.