Abstract: In view of problems of low efficiency and large dosage of fatty acid as collector in desilication by direct flotation of bauxite，a new synergistic agent DT for fatty acid is prepared to enhance the collecting performance. Conditioning tests of coarse flotation for desilication was carried out on a low Al/Si ratio diasporic bauxite using oleic acid synergist with synergistic agent. The results show that the optimum ratio of DT to oleic acid is 2∶8. Adopting this ratio，Al₂O₃ recovery of rough concentrate by using DT + oleic acid at 500 g/t is 8.90 % higher than that by single oleic acid at 500 g/t，while dosage of oleic acid should be increased to 800 g/t to achieve the same concentration index as mixture ratio of DT + oleic acid at 2∶8. The closed circuit operation on the basis of rough concentration and open circuit process are carried out. It is shown that using sodium carbonate as pH modifier，DT + oleic ratio of 2∶8 as collector，at the grinding fineness of 74 μm passing 93%，Al/Si ratio of the ore is increased from 3.27 to 8.13 with Al₂O₃ recovery of 76.67% through one roughing，two cleaning flotation，while the total dosage of DT + oleic acid is only 800 g/t. To sum up，the synergistic agent DT can significantly increase the performance of oleic acid.

Key words: Bauxite, Desilication by direct flotation, Oleic acid, Synergistic agent DT