Abstract: Due to effect of the activation of metal ions on gangue minerals in Bayan Obo rare earth dressing plant，the flotation process of one-roughing and two-cleaning can not form a closed-circuit flow-sheet，leading to an unfavorable flotation index (middles return makes the flotation system difficult to keep stable). In order to solve the problems of poor stability in production process and undesirable production index，optimization tests of reagents for the on-site rare earth floatation were made. The results showed that the combining inhibitors of citric acid and sodium silicate of gangue minerals can effectively eliminate the activation of metal ions on gangue minerals; With the usage of citric acid and sodium silicate at 200 +1 500 g/t，rare earth concentrate with ReO grade of 51.32% and recovery of 70.94% was obtained by adopting the process of one-roughing，two-cleaning and middles back to the flow-sheet in turn. Compared with on-site index，ReO grade and recovery rate were increased by 1.32 percentage point and 15.91 percentage point respectively.

Key words: Rare earth, Inhibitor, Complex agent, Sodium silicate, Citric acid