Abstract: This paper discusses instability water conductivity reasons of coal pillar from three coal pillar failure modes after mining at both sides of coal pillar faces, including stress redistribution water conductivity, upper three zones water conductivity at mining face and lower three zones water conductivity at both sides of coal pillar. The methods of increasing width of waterproof pillar, grouting, blocking fissure water guide channel are put forward to avoid coal pillar water conductivity in mining area.