Abstract: In order to study ground movement deformation law in backfill mining，the impact of ground movement and deformation five indicators caused by underground mining on surface buildings are briefly introduced，the inner link between the five indexes and the direct cause of the damage to surface building is analyzed.Based on this，the conceptions of surface “subsidence gradient” and “horizontal displacement gradient” are introduced，thus a new evaluation index for filling mining effect and requirement is put forward.On the premise of slowing down the surface subsidence and horizontal movement at the same time，it's necessary to focus on the control of gradient.FLAC3D numerical model was set up based on field conditions of the tenth mining area 10203 backfill working face in Xinyang mine and the contrastive analysis of surface movement gradient variation rule between filling method and caving mining method was conducted.Research has shown that the backfill mining reduced the amount of surface subsidence and horizontal movement，significantly lowered the surface subsidence and horizontal displacement gradient.The surface tends to keep uniform movement and continuous deformation，which can effectively guarantee the safety of buildings.

Key words: Backfill mining, Ground movement deformation, Subsidence gradient, Horizontal displacement gradient, Building protection