Abstract: The stress model of roof was established based on the elastic foundation beam on the basis of the analysis of breakage migration laws of stope basic roof. The calculation formulas of the first weighting interval and the periodic weighting interval were obtained. The results show that when the limit span of the seams above the roof strata is less than the limit span of the basic roof of the working face, the first weighting interval is equal to the initial roof caving step distance, and the periodic weighting step distance associates with the upper strata thickness and bulk density, tensile strength and other parameters; when the limit span of a layer roof above the basic roof is greater than the limit span of main roof, the first weighting interval is equal to the sum of the two caving steps of the basic roof, and the periodic weighting step distance is related to the resistance of the support.