In this article, an innovative backfill material is introduced as a green material largely utilizing two major coal mining waste: coal refuse and coal sludge. Coal refuse is rock-like solid waste, comparatively, raw coal sludge is slurry. A smart recipe design of backfill material was introduced, which contains only 1 % of cement and the rest 99 % of raw material is from industry waste. The backfill material at 75 % pulp density shows excellent performance such as high unconfined compressive strength, great flowability, and low bleeding rate. Also, the article discusses the morphology change of the backfill harden body during different curing ages, the observation through SEM-EDS illustrates the distinguished morphological characterization of the needle-like ettringite and amorphous gel. Furthermore, TCLP results indicate that this designed backfill material is environmentally acceptable and none of the heavy metal leaching has over the limitation by US Environmental Protection Agency (EPA). © 2012 Springer-Verlag Berlin Heidelberg.