Abstract: In view of the high cost of using cement as cementitious material for filling in Jinchuan Mine，new cementitious materials for mining are developed by utilizing local solid waste resources.Firstly，the physical and chemical analysis of the test materials is carried out，the orthogonal test of the strength of phosphogypsum-slag composite cementitious materials is done， and on this basis， the optimum proportion of phosphogypsum-slag composite cementitious materials is determined by the optimum test.Then，the factors affecting the strength of phosphogypsum-slag composite cementitious materials are analyzed， the microstructure of hydration products at different ages is observed by scanning electron microscopy，besides that，the cost of phosphogypsum-slag composite cementitious materials is calculated.The study results show that the early strength of phosphogypsum-slag composite cementitious material is lower than that of later strength； the optimum ratio of phosphogypsum-slag composite cementitious material is determined by optimizing the ratio of 7% quicklime， 30% phosphogypsum， 2% mirabilite and 61% slag powder； SEM showed that ettringite and C—S—H gel are the main hydration products， and with the growth of curing age， the structure became close and the strength increased continuously；and the cost calculation of the optimum ratio of phosphogypsum-slag composite cementitious material is carried out. The cost of cementitious material is 180 yuan/t， which is 44% lower than the cost of 38.5 non-standard cement used in Jinchuan Mine.The pipeline transportation characteristics of composite cementitious material filling slurry are measured， and the results can meet the requirements of gravity transportation in Jinchuan Mine.

Key words: filling mining method, phosphogypsum, slag, cementitious material, optimization, hydration mechanism