Abstract: Based on the engineering background of 12418 working face of a coal mine, we established “coal pillar-backfill-coal wall” mechanical structure model by theoretical analysis, and analyzed the interaction relationship between the backfill and surrounding rock after the goaf filling. By establishing two-dimensional discrete element by UDEC, we analyzed the effect of reducing surface subsidence between backfilling method and caving method. The results show that overlying strata load was supported by multiple support points by using filling method, the deflection value of roof decreased；maximum ground subsidence coefficient was low, the instability of opencast bench did not occur in roof. The overlying strata motion was effectively controlled, surface subsidence was relieved and surface building was protected by using the filling method.