Abstract: Coal pillars generally experience instability problems in the section of fully mechanized caving face.A case study was performed at the 25 m coal pillar in the ZF211 working face of Jiangjiahe Coal Mine.The function relationship between the ultimate energy and lateral stress of the coal pillar were analyzed through theoretical analysis,numerical simulation and field tests.The instability criterion of the elastic zone in the coal pillar was proposed,and the influence of the plastic zone range and the effective width on the ultimate energy of the elastic zone was studied.The results showed that the ultimate energy of the elastic zone had a quadratic positive correlation with the lateral stress,and the lateral stress was distributed symmetrically in an "upward convex" shape.The size of the"upward convex"shape increased with the extent of the plastic zone.The ultimate elastic energy density increased with the extent of the plastic zone and the effective width of the coal pillar.The elastic energy within the coal pillar was distributed in a "bimodal" pattern,which increased with the extent the plastic zone.Two forms of energy accumulation instability were proposed,local impact and large-scale chain impact.The corresponding control technology was put forward and applied in the field.The engineering practice showed that the control effect was good.