Abstract: Taking phosphate tailings in Guizhou as the aggregate, fly ash and cement were used as cementitious material to prepare cemented filling slurry. The effect of different amounts of citric acid on SO₄^2-, F^- in filling slurry bleeding and the bleeding rate was studied. The extended degree method, the fluidity method and the L tube method were employed to study the effect of different amount of citric acid on the flow performance of phosphate tailings slurry. The results showed that adding citric acid resulted in the increase of SO₄^2- and decrease of F^- in slurry bleeding, but had little effect on the bleeding rate. In addition, citric acid exhibited a retarding effect on the filling slurry, which could improve the fluidity of the slurry.