Abstract: Combining with the special production geological condition of 1126 filling face, strata behavior law was discussed by theoretical calculation, numerical simulation and field measurement. The critical breaking filling height of main roof was confirmed by thin plate theory. FLAC3D software was applied to analyze the law of plastic zone distribution and vertical displacement sinkage of the roof strata on fully caving mining method and high water filling method. The measured data show that strata behavior of backfill mining with high water material was relaxed. Working resistance of hydraulic support was low as a whole, the surface deformation value was controlled within the scope of the damage at level I.