Abstract: In order to improve the properties of backfill material in coal mine, a kind of backfill material that takes coal gasification coarse slag and super-fine sand as aggregate and ordinary Portland cement as cementitious material is used. The slump and strength of the backfill material were measured. The results show that with the increasing of super-fine sand, the slump of the slurry decreases; the strength of the backfill material attains the most when the uniformity coefficient of the aggregate conforms to Talbot formula（K₀=4 to 5）. The super-fine sand is better than the coal gasification fine slag as fine aggregate when coal gasification coarse slag is used as coarse aggregate and content of Portland cement is 8% in the backfill material.