Abstract: The cementation self-reliance strength theory of previous filling is modified and the calculation formula for artificial key filling layer's thickness is derived to get more economic and reasonable the key filling thickness.Based on making sure the production safety in working faces，the slicing and filling can has a positive effect on costs saving.Meanwhile，it can also provide an effective way for realizing the recovery of coal resources from the damaged area of small pits.

Key words: Cementing filling, Stratification, The key layer, Self-reliance strength