The invention discloses a process of for producing methane by cooperative metabolism of biomass injected into a waste mine and residual coal. The process comprises the following steps: (1) selecting ato-be-discarded mine or a discarded mine; (2) selecting a working face with more residual coal or a safe coal pillar as a test point; (3) treating surrounding rock cracks and roadway engineering so as to form a relatively independent closed space; (4) establishing two passages connected with the ground; (5) injecting the biomass into the closed space under the mine through the preset passage after the mine is closed; (6) gradually soaking the residual coal and the biomass in mine water as the time of closing the mine is prolonged, monitoring gas production rate, total gas production amount and gas components through a produced air overflowing passage; (7) evaluating the effect of producing the methane by the cooperative metabolism of the biomass and the residual coal. The process providedby the invention uses methanogenic flora widely existing in the waste mine water, promotes the cooperative metabolism of the biomass and the residual coal to produce the methane, improves the utilization rate of the residual coal and the amount of biomass gas production, and realizes the aims of turning waste into treasure and energy saving and emission reduction.