Abstract: In order to solve the problems of environmental pollution and land occupation by direct stock of Phosphate Tailings(PT) from dense medium separation of Tiaoshuihe Phosphate Plant，Sanning Mining，Hubei Province.Feasibility tests of PT used as cementing material for filling in mining operation was conducted on the basis of its property measurement.Results indicated that：coarse PT can be used as cementitious material for its roughness surface and low content of harmful elements；Compressive strength of backing filling body in each age enhanced with the increase of cement-sand ratio and slurry concentration，while slurry concentration has more influence on compressive strength of filling body；filling pulp slump，slump flow and consistency all increased with the increase of cement-sand ratio and slurry concentration.In order to further reduce the cementing material cost，feasibility of cement partly replaced by Fly Ash(FA) as cementing material orthogonal experiment were conducted.The results showed that：addition of FA is beneficial for the strength enhance of filling body，especially long-term strength；filling slurry slumps first increase and then decrease with the increase of cement-aggregate ratio，slurry concentration and dosage of FA，and the impaction weakened by cement-aggregate ratio，slurry concentration，dosage of FA.FA can play a role in ball bearing effect for its fineness particle sizes and partly in spherical form，thus reduce the friction between phosphate tailing particles and improve the workability of slurry；there are so many internal spaces inside the FA，with the dosage increase of FA，water demanding also increases，which resulted in the viscosity increase of the filling pulp，hindered aggregate moving in the slurry，consequently，both slumps and consistence show first increase and then decrease rule with dosage of FA.The optimum ratio of cementitions mateials are cement aggregate ratio 0.250,sturry concentration 80%,dosage of FA 1.00.Using PT and FA in cemented backfilling industry has significant economic，environmental and social benefits.

Key words: Fly ash(FA) , Coarse phosphate tailings, Cemented paste backfill, Orthogonal experiment