In order to analyze the stability of the filling body along gob-side entry of the Xinyuan Mine, the numerical simulation method for analysis and research was adopted. First of all, a numerical simulation model according to the mining conditions and geological conditions of Xinyuan Mine built by FLAC3D numerical simulation software, according to the physical and mechanical parameters measured in the laboratory, and seven groups of simulation calculation schemes according to the purpose of simulation were designed. The physical and mechanical characteristics of the post-mining filler were simulated, and the effects of width on the stability of the filler and compressive strength on the stability of the filler were analyzed. The results showed that the larger the width of the fill body, the smaller the deformation of the roadway surrounding rocks, and the more utilization of the roadway maintenance; the larger the fill strength, the more favorable to the maintenance and use of the roadway.