Abstract: In view of the ultra-fine full tailings of Gaoguanying Iron Mine， the research on high-strength and low-cost new filling cementing materials for cement replacement was carried out with cement， lime， desulfurization gypsum and slag as raw materials in the surrounding area of Tangshan City.The strength test of cement，lime and desulfurization gypsum cementitious materials was carried out by orthogonal test design. The range analysis shows that the order of influence of the strength of the new cemented material cemented backfill 7 d is cement，lime，desulfurization gypsum.The optimized strength formula of the filling body 7 d is 3.5% cement， 2.5% lime，17.5% desulfurization gypsum，2.79 MPa strength，about 5.3 times that of 32.5R cement.The strength of the cemented backfill 28 d is opposite to that of 7 d.The 28 d strength optimization formula is 4.5% cement，2.5% lime，17.5% desulfurized gypsum，and 5.04 MPa，which is about 4.5 times that of 32.5R cement.The SEM electron microscopy analysis results show that the dominant hydration products of the new cementitious materials are ettringite and C-S-H gel.The increase of cemented backfill strength is the result of the continuous formation and development of these two hydration products.The rheological property test of the mortar shows that the new cementitious material filling slurry with a mortar concentration of 68% reaches the Bingham body fluid state and is suitable for slurry pipeline transportation.On-site industrial tests show that the strength of the new cementitious material filling body with a mortar ratio of 1∶5 and a mortar concentration of 68% is 4.91 MPa，which meets the design principle requirements of the 28 d strength of the lower filling body of the filling road，which is greater than 4 MPa.The error of the indoor test is 2.6%，which indicates that the test data obtained by the indoor test is relatively reliable，and the strength performance and the topping rate are better than the 32.5R cement，which provides a strong guarantee for safe and efficient filling operation of the mine.

Key words: Underground mining, Filling mining, Ultra-fine full tailings, Orthogonal test, Strength of filling body, Hydration mechanism, Rheological properties