Shanjiaoshu Mine 22155 working face was taken as the engineering background, according to the engineering geology condition of the working face and the relation of upper and lower working face mining in coal seam group, using numerical analysis method to calculate the internal stress concentration factor of 22153 goaf edge coal body, and based on the elastic-plastic mechanics theory, a computational formula for the reasonable width of coal column was put forward. The results show that the roadway side plastic zone width calculate by limit equilibrium theory is more reasonable than the one directly calculated by using the bolt length. And that in complex coal seam mining conditions, the stress concentration coefficient is obtained by the method of numerical analysis. And the field practice proves that coal pillar width calculated by the formula for complex coal seam mining conditions is scientific and reasonable.