Given the problems existing in the ultra-fine ungraded tailings,such as slow dehydration speed,easy mixing of overflow,high viscosity,and poor filling strength,Zhongguan Iron Mine has carried out research,such as particle size test and chemical composition analysis of the ungraded tailings,natural sedimentation test and flocculation sedimentation test of the ungraded tailings,research on coordination and connection of separation and filling processes,research and development of steel slag-based cementitious materials,and the configuration of the paste-like filling process with ultra-fine tailings.The on-site system commissioning shows that the green paste-like cemented filling technology and process with ultra-fine ungraded tailings are reasonable,and the filling body strength is 2.8-2.9 MPa,meeting the strength requirements of the underground filling body.