The conventional collector for diaspore mineral is oleic acid, which is highly insoluble and must be used in high dosage in bauxite flotation, that is the great drawback of oleic acid in use. Octylic hydroxamic acid was synthesized, and its collecting ability to certain minerals in bauxite： diaspore and kaolinite were studied. The collecting power of various reagents to diaspore in an incremental sequence was shown as follows ： oleic acid 〈 octylic hydroxamic acid, while the incremental sequence of the collecting power to kaolinite was like this ： octylic hydroxamic acid 〈 oleic acid. It could be seen that octylic hydroxamic acid had the capability of high collectivity and good selectivity, and octylic hydroxamic acid was chosen to use in the following experiments. Reduced zeta potential showed the adsorption of the an- ionic collector on the mineral. By the adsorptive capability and IR（ infrared ray） tests, the adsorption of octylic hydroxamic acid on diaspore was determined to be chemical absorption, which was greater than that of oleic acid, as it was absorption by hydrogen bond.