Abstract: The shallow coal resources have been almost completely excavated,and the coal mines are gradually extending to the deep coal-bearing strata currently. Due to the threat of “high temperature,high pressure and high gas” and complex geological structure in the deep strata,the underground operation environment becomes very harsh. Although the deep concealed fault structure,which has a great influence on the safety production of coal mine,is explored by drilling,geophysical exploration and roadway excavation,the basic information of fault properties and fault activation under the disturbance of mining isn’t well grasped by the mine. In the stage of designing the retaining size of fault coal (rock) pillars,the problem of retaining size of fault coal (rock) pillars is usually too large or too small,which leads to the decrease of coal resources during production,or the fault water disaster induced by fault activation. Taking F6 fault of Jiigou coal mine of Suzhou Coal and Electricity Group as the research target,this paper comprehensively analyzes and studies the width of waterproof coal pillar in coal seam from the aspects of water-containing/conducting properties of faults,characteristics of faults activation under the disturbance of mining,lithological characteristics of coal seam roof and development height of water-conducting fracture zone. Utilizing COMSOL Multiphysics (CM) numerical simulation based on finite element theory,theoretical calculation and mine production verification methods,the most reasonable size of waterproof coal pillar is determined. The study shows that F6 fault is featured by weak water abundance and poor water conductivity in undisturbed state. However,when the working face continues to advance 20 m away from the intersection line of fault and coal,the rock strata near the fault zone suffer plastic failure due to concentrated stress,and the water conductivity of the fault changes. On the foundation of the above comprehensive analysis,it is finally determined that the reasonable reserved width of waterproof coal pillar of F6 fault is 36.13 m. The results of this study provide a certain technical guarantee for the maximization of safety and economic benefit in Jiegou coal mine.