This paper aims to analyze the roof stability when the reclaimed working face passes through abandoned roadway. The mechanical model of main roof in abandoned roadway was established for the purpose of theoretical analyses. To ensure the stability of the abandoned roadway, the strength formula of backfill body was deduced. The optimum ratios among different compositions of the filling material were determined by experiment, while the viscosity, bleeding, hydration temperature and compressive strength of filling material were also studied. Test results indicated that the optimum ratio among coal ash, lime and compound activator is 80:15:5, and the ideal water cement ratio is 0.7:1. It was also found that no bleeding occurred, the rheological behavior of slurry presented shear thinning fluid and the hydration temperature of filling body was relatively stable which is mainly maintained at 40°C. The uniaxial compressive strength of filling material with 28 and 90 days curing were 3.35 and 6.62 MPa respectively. Under a confining pressure environment, the filling material presented an obviously plastic deformation. Field test showed that the filling rate was almost 100%, when working face passed through abandoned roadway, the surface of filled body was complete and no roof collapse was triggered. Therefore, a better bonding effect was proved for the filling body.