Abstract: Aiming at the problems of coal roadway large-range deformation and breakage caused by unreasonable coal pillar dimension in fully-mechanized working face with thick coal seam. Taking advantage of the engineering analogy theoretical analysis and numerical simulation to find the reasons for the instability of roadway and the reasonable width of coal pillar. In the spot, coal pillar optimization experiment was carried out to verify the results. The results show that it was not suited for narrow coal pillar under the conditions of geological and production in Chahasu coal mine. It is proved that the main existed difficult problem of roadway support was caused of small pillar width for roadway maintenance has caused the bearing stress superposition issues. Through compared with the distributing rules of stress, displacement and plastic zone distribution with different coal pillar width, ultimately arrive at the conclusion of the coal pillar width is 35m, and this optimization design has an obvious advantage in engineering and economic terms.