Abstract: The stability of roof is the main factor to determine the safety of mining face in the underhand slice stopping with cemented filling method. Taking a mine as engineering background, the stress, displacement, plastic zone and the force characteristics of steel were analyzed to study the roof stability of cemented classifying tailing by new cemented agent using the means of combining field monitoring with numerical methods. The result shows that the steel reinforcement has a great effect to backfill of the whole body; and when the mass ratio are 1 to 6 and 1 to 12, the new cemented agent materials are batter than the 42.5 grade cement agent material with the mass ratio of 1 to 4 and 1 to 8; according to the numerical calculation results and field monitoring, the new cemented classifying tailings can meet the requirements of filling stope roof stability.