Abstract: The depressing effect on diaspore is the key of removing silicon from bauxite of low Al2O3/SiO2 by reverse-flotation.The effect on diaspore and kaolinite were investigated on the different condition by using a industry waste bacteria as depressor .The results show,it is obvious that the depressing effect of the industry waste bacteria on diaspore,but the bacteria has little effect on kaolinite.The effect of industry waste bacteria is better than starch which is usually used as depressor of diaspore by comparing experiment.so index of separating aluminum and Silicon is improved by using industry waste bacteria as depressor.The function mechanism of the industry waste bacteria on separating aluminum and Silicon was studied.

Key words: Waste bacteria, Diaspore, Kaolinite, Reverse-flotation, Depressor