Abstract: After entering the second stage mining in north mining area of Xishimen Iron Mine，the left incline shaft only as a downcast，allowing a large deformation，but not allowed to fall off，so the protection level is reduced and reduced the protection scope,meanwhile the basis of determining the scope of protection is changed from moving angle to collapse angle.Filling the collapse pit with waste rock in time can improve the collapse angle，the collapse angle can be increased to 75° when the granular filling depth reaches the critical granular column hight in north mining area.Redelineate the safety pillar with 75°subsidence angle to replace rock moving angle which is 60°，thereby a significant amount of pillar ore is released.The released pillar ore have been mining with no pillar sublevel caving mining method or inducd failing with trench bottom structure mining method，and have achieved marked technical and economic results.

Key words: Granular column support, Rock movement control, Delineation of satety pillar, The improvement of subsidence angle