To take full advantage of gangue for roadside supporting in coal mines physical properties of coal gangue are tested. The collapsed slump uniaxial compression strength and initial setting time of gangue binder backfill material with different water-cement ratios and admixture contents are researched. Experimental studies show that the best ratio of water cement coarse aggregate fine aggregate and admixtures is 1:2:5.6:1.6:0.02 for site pumping of roadside packing support. The collapsed slump 28 d uniaxial compression strength and initial setting time of gangue binder backfill material are 210 mm 20.8 MPa 224 min respectively under such ratio. It could satisfy the requirement of site supporting and the initial setting time of binder backfill material under such ratio is about 50 min shorter in site than indoor.