Abstract: In this paper, the effect of the grinding fineness and the reagent regime on the flotation of low grade calcareous-siliceous phosphate in Guizhou was investigated by using the collector AY and GJBW. The results showed that when the grinding fineness was 78.08% below 0.075 mm, the optimal reagent regime was 7.5 kg/t mixed acid (sulphuric acid and phosphoric acid volume ratio of 2:1) with 0.3 kg/t GJBW for roughing, and 7.5 kg/t mixed acid with 0.4 kg/t AY for concentrating. Under these conditions with the double reverse flotation test procedure, final flotation phosphate concentrate with phosphorus pentoxide grade of 30.27% and recovery rate of 81.32% was obtained. The results of orthogonal tests showed that the interaction among mixed acid, GJBW and AY had little effect on the concentrate. The results of FTIR analysis showed that the adsorption of AY onto quartz was mainly physical adsorption.