Abstract: In terms of fully mechanized mining roadway with large fault waterproof pillar which will influence working face system distribution seriously and decreasing coal mining rate, in this article, it states fault waterproof pillar optimization research. According to research optimization of Yiqiao Coal Mine YF_20-3 fault waterproof pillar by the way of exploration drilling and tunneling prospecting confirming no water and no water transmission. It theoretically simulates the minimum width of 47 m. Combining Grey Correlation Analysis and LMBP neural networks builds integration evaluation model to value stability of fault pillar. When coal pillar width is no less than 10 m, it is safe and stable. The article proves the evaluation model results and analyzes the stress and failure regularity during the process of advancing coal face with FLAC^3D and it confirms that estimated optimization width is 10 m for YF_20-3 fault pillar. By the way, during the process of 13-04 working face mining there is no big scale damage and crossheading operates well.