Abstract: In order to solve the environmental pollution problem caused by desulfurization ash slag accumulation， and to use it and other solid waste as the main raw materials to produce low-cost filling materials for underground mine filling. The filling material's performance test， and the hydrated products of the filled test pieces were analyzed by SEM， on the basis of modifying the desulfurization ash slag， the modified desulfurization ash， reinforcing agent， gypsum， slag and tailings were used as raw materials. The results show that:① Modifier CHJ-1 can reduce the content of CaSO3 in desulfurization ash by 48.30% when the dosage is 2%， the modification temperature is 120 ℃， and the modification time is 12 h. ②The change of the amount of modified desulfurization ash has little effect on the fluidity of the filling slurry. The content of modified desulfurization ash increased from 10% to 15%， the shrinkage rate of filling slurry decreased significantly， and the compressive strength of specimens of various curing ages increased significantly. The amount of modified desulfurization ash continued to increase to 20%， the shrinkage rate of the filling slurry was significantly increased， and the compressive strength of the specimens of various curing ages was significantly reduced. When the content of modified desulfurization ash is 15%， the filling degree of filling slurry is 152 mm and the shrinkage ratio is 1.41%. The compressive strength of filling specimens is 1.28 MPa and 2.86 MPa for 7 d and 28 d， respectively. And can match downhole filling requirements. ③Modified desulfurization ash could successfully stimulate the hydration reaction of slag. The hydration products are mainly rod-shaped ettringite and cluster-like hydrated calcium silicate gel， and the space network structure formed by interpenetrating them makes the filling specimens has structural strength， and as the curing age increases， the number of hydration products increases， and the compressive strength of the filling specimens increases.

Key words: Desulfurization ash, Blast furnace slag, Tailings, Modified, Filling material