Abstract: A systematic understanding of the action mechanism and reasonable parameters of the backfill body in the process of overlying rock movement is an important premise to ensure the safe use of goaf roadway. In order to ensure the stability of gob-side roadway and safe mining of the working face in the lower section, based on the analysis of the interaction mechanism between the backfill body and the overlying rock in the process of overlying rock movement, the parameters of the backfill body are analyzed and applied in the field through theoretical analysis and numerical simulation. The results show that the backfill in the roadway side can be divided into early active support stage, transitional pressure support stage and late maintenance stage according to the different mechanism of overlying rock movement. When the supporting resistance of backfill body is constant, the strength of backfill body is inversely proportional to its width. The filling body with 2 m width, 3.13 MPa strength and 5 MN/m support resistance can meet the site requirements. After the field application, the deformation of the surrounding rock of the roadway is controlled within a reasonable range after the deformation is stable, and the application effect is good.