Goaf filling rate directly influenced surface subsidence, was one of the important index to estimate filling mining effect. Filling mining was widely used in Fengfeng Group, the result showed that roof subsidence, short of top amount, filling body compression resistance were key factors to affect gangue paste filling mining recovery working face filling rate. Through improving the coal cutting process, optimizing the filling process, adjusting the ratio of slurry, effectively improved goaf filling rate and ensured filling effect.