Abstract: In order to study the rationality and feasibility of waterproof coal pillar of large fault for a working face in Chengjiao Coal Mine, on the basis of reference literatures, the engineering geological model was established for the relationship between the working face and large fault. In both cases, considering the range of mining failure zone and without considering fault fracture zone, the retention value of large fault waterproof coal pillar was calculated in combination with the relevant specification, the maximum value was greater than the width specified by Yongcheng Coal Industry Company in 2006, the biggest difference was about 227.5 m. Finally, by comparing with the actual width of the actual set, it was found that the calculation result was closer to the actual condition of the mine when considering fault width and mining floor damage zone.