Abstract: In order to solve the related technical problems of low filling concentration and low filling strength of fine-grained tailings in the filling process of Zhongguan Iron Mine，the physical and chemical properties of filling aggregate，the flocculation sedimentation test of fine-grained tailings，the strength test of different cementitious materials of fine-grained tailings and the strength test of different cement-sand ra⁃ tio of fine-grained tailings are studied，and the technical transformation scheme of filling system is put for⁃ ward. The final field results show that when the fine-grained tailings cement-sand ratio is 1∶5，the 3 d uni⁃ axial compressive strength of the filling body is ≥ 1.0 MPa，the 7 d compressive strength is ≥ 1.5 MPa，and the 28 d compressive strength is ≥ 2.5 MPa，which fully meets the two-step mining demand of Zhongguan Iron Mine. It not only solves the problem of fine-grained tailings discharge，reduces the pressure of the filter press workshop，but also improves the utilization rate of tailings.

Key words: filling system, filling body strength, fine-grained tailings