Water quenching blast furnace slag was chosen to produce a neotype whole tailing cementitious material with using lime and desulphurized gypsum as composite activator and adding small amount of admixture. The effect of different use level of composite activator on the compressive strength of neotype whole tailing cementitious material backfilling body was investigated. Compositions and microstructures of hydration products of neotype whole tailing cementitious material were studied by X ray diffraction and scanning electron microscopy. Results show that as the mix proportion(by mass) of the cementitious material is 4.0% lime, 17.5% desulphurized gypsum, 0.5% admixture, 78.0% water quenching blast furnace slag, the mass ratio of the cementitious material to whole tailing being 1∶8 and the concentration(by mass) of backfilling slurry being 68%, the compressive strength of the neotype whole tailing cementitious material backfilling body is 3.09MPa when cured for 28d, which is 7.2 times that of 42.5R cement backfilling body at the same concentration(by mass) of backfilling slurry, same mass ratio of the cementitious material to whole tailing and same mass proportion of admixture. The neotype whole tailing cementitious material can replace traditional cement in whole tailing backfilling. Hydration products of the neotype whole tailing cementitious material are mainly ettringite crystal and C S H gel.