The invention discloses a method for filling a gas near a roadway of coal mine gob-side entry retaining, comprising the following steps: firstly, arranging a gas pressurization room on the ground; then, arranging a gas booster pump in an underground mining area haulage roadway 3; arranging a cylinder rubber air sac as high as the mining height on one side close to a goaf along the gob-side entry retaining behind a coal face; aerating the cylinder rubber air sac arranged on one side close to a goaf by the gas booster pump until roof contacting; when the pressure gage of the gas booster pump displays that the pressure reaches the stress of a primary rock, stopping aerating, sealing the cylinder rubber air sac to finish the aeration operation of one cylinder rubber air sac; and when the coalface is continuously advanced, continuously arranging one cylinder rubber air sac behind one aerated cylinder rubber air sac every time the coal face is advanced by one step, and aerating one by one until one exhausting body on one side of the goaf 5 along the gob-side entry retaining 6 is filled and supported. The method is simple, is convenient to operate and has the advantages of small labor intensity of workers and good supporting effect.