Abstract: In order to study coal broken laws ahead of working face in extremely thick coal seam, based on Qianqiu Coal Mine 21121 working face geological conditions, comprehensive study was done by the method of comparison analog simulation and field test. The Results show that broken degree of the coal mass is increasing from the bottom to the top in the same distance, and broken degree is also increasing with distance becoming closer at the same horizon; with the increasing of coal thickness, coal can form inverted triangle fully broken and equilateral triangle adequately broken layers; mining the lower coal of special thick coal seam advancing abutment pressure extremism points is relatively close to working face, and abutment pressure extreme value is less than the upper coal; with coal thickness increasing, advanced abutment pressure extremism points gradually decrease and overall broken degree of advanced abutment pressure on coal is reduced.