Abstract: The mining technology with coal gangue backfilling can be used to recover the resource of “three under” underground coals and the coal pillar by the way of low cost,high security and effection.Effective recycling of gangues in mining area is the key for green mining.The theory of equivalent mining volume of trapezoidal strips filling mining strata control is presented.A further analysis of the determination of size and stability are made.The results show that: stability of filling reduces with the increase of mining depth and mining height,and increases with the increase of filling body's sectional dimension.The trapezoidal backfilling method is suitable for medium-thin coal seam with small mining height,and the dense backfilling is more suitable for the thick seam mining with large mining height.

Key words: Trapezoid strip filling, Equivalent mining volume, Stability of filling body