Abstract: The main phosphorus mineral of a low grade phosphate ore with high silicon and magnesium in Guizhou is collophanite which consisted mainly of fluoroapatite and partly of carbon-apatite. And the main gangue minerals are quartz， dolomite， illite and pyrite， etc. The grade of P₂O₅， SiO₂， CaO and MgO is 26.19%， 16.88%， 38.18% and 1.92%， respectively. In order to determine the development and utilization process of ore， the experiment was carried out using double reverse flotation process. The results showed that under the grinding fineness of 82.05% -0.074 mm， with the process of preference reverse flotation to remove magnesium-sedimentation to remove slurry-reverse flotaion of one roughing two cleaning and tailings of roughing and first cleaning returned after mixed and via one scavenging of silicon remove process， the phosphorus concentrate with P2O5 grade of 32.35%， P₂O₅ recovery of 82.36%， MgO to P₂O₅ ratio of 2.32%， R₂O₃ to P₂O₅ ratio of 11.07% could be obtained. The bubbly， sticky and intractable foam in cationic reverse flotation process can be solved by desliming before desilication and the use of T609 combined with defoaming agent TOP. Double reverse flotation makes apatite separated from gangue mineral and acquires the concentrate which reaches the high-class standard of phosphate ore for the acidic process.

Key words: Phosphate ore, Double reverse flotation, Fatty acid, Ether amine, Over-stable froth