Abstract: For problem that coal pillar is treated as a continuum in most of the coal pillar deformation studies without considering structural plane damage and instability in coal pillar, numerical simulation of the maximum principal stress and deformation of coal pillar under different inclinations and spaces of structural plane were carried out by use of 3DEC software. The results show that the maximum principal stress of coal pillar increases with increase of space of structural plane and decreases with increase of inclination of structural plane; influence of space of structural plane on the maximum principal stress of coal pillar decreases with increase of inclination of structural plane; coal pillar deformation decreases with increase of space of structural plane and increases with increase of inclination of structural plane; coal pillar deformation increases significantly when space of structural plane is less than 1.5 m and inclination of structural plane is more than 45°.