In order to improve the recovery rate of coal resources and dispose of a large amount of coal-based solid waste, based on the integration of excavation and filling of inter-surface coal pillars, considering the influence of curing age on the strength and bearing capacity of the filling body, the evolution law of the strength of the filling body with age under different cement contents was studied through laboratory tests. It was found that the cement content was positively correlated with the strength of the filling body, and the strength of the filling body increased exponentially with the age. According to the difference of the strength of the filling body, the bearing state of the filling body to the roof was divided into three stages : short-term bearing, medium-term bearing and long-term bearing. By establishing the collaborative bearing model of backfill-roof with different strength at different ages, the roof deflection equations of each region in the process of ' excavation-filling ' are given. A numerical simulation model of backfill-roof collaborative bearing was established by FLAC3 D. The effects of cement content, excavation-filling distance and excavation-filling speed on the stress of backfill and roof subsidence were analyzed, and the evolution law of backfill-roof collaborative bearing under different excavation distances in the process of ' excavation-filling ' was explored.The results show that in the process of ' excavation-filling ' of inter-surface coal pillars, the higher the cement content and the smaller the excavation-filling spacing, the faster the strength formation time of the filling body, the greater the vertical stress of the filling body and the less the roof subsidence. The faster the excavation and filling speed is, the shorter the curing age of the filling body in the filling area is, the lower the strength is, the worse the bearing effect is, and the plastic zone of the filling body and the roadway roof is seriously damaged. With the increase of tunneling distance, the maximum subsidence velocity of roof decreases gradually, and the cooperative bearing structure of backfill-roof tends to be stable gradually.