Abstract: REO content of tailings from calcium roasting-low intensity magnetic separation tailings from Bayan Obo Plant low intensity magnetic separation-high intensity magnetic separation-flotation was 12.27%.Main components is rare earth oxides，fluorite，small quantity of fluorapatite and quartz.Hydrochloric acid was adopted to study leaching rare earths in material and relevant processing parameters were studied.The results indicated that:when hydrochloric acid concentration is 1.5 mol/L，leaching temperature is 45 ℃，ratio of liquid to solid is 10∶1 mL/g，leaching time is 60 min，stirring rate is 300 r/min，leaching rate of rare earths could reach 93.15% and the leaching ratio of fluorine was only 0.23%.Under the low leaching ratio of fluorine premise，the rare earth could be efficiently leached.

Key words: Bayan Obo tailings, Hydrochloric acid leaching, Rare earths