Abstract: In coal mining with backfill, backfill material dominates the benefit, efficiency and effect. In order to get the characteristics varying pattern of cemented and high concentration backfill material with wind-blown sand as aggregate, fly ash is selected as variables to test and analyze the characteristics varying pattern of backfill material with the mix proportion of fly ash. The results show that, as the mix proportion of fly ash increases in a proper range in backfill material, the compressive strength increases, the bleeding rate decreases in general, the layered degree declines by linear pattern, the coagulation time grows up by exponential pattern, and the slump is growing consecutively. But, with the higher mix proportion of fly ash, the compressive strength and slump will drop comparatively. When the mix proportion of fly ash is in proper range, the fly ash optimizes the particle size gradient of backfill material, and makes water and cement distribution uniform in backfill material. As a result, the strength characteristic and rheological performance can be improved. However, some characteristics will degenerate with higher mix proportion of fly ash.