Abstract: The mechanical problem of the filling body is simplified to the plane strain problem because of the length of the ore body is much larger than the size of the stope, and the internal shear stress expression of the filling body under one side exposure is derived.Combined with the mining technical conditions of Aoniu iron mine, and through the analysis of the relationship between the bottom shear stress of different proportions of filling body and the height and width of the mine, it is determined that the height of the mine and the pillar is 40 m and the width is 40 m and 30 m respectively.The research results can provide theoretical basis for similar metal mining.