Bismuth oxide micro-powder and its preparation method

The invention discloses a bismuth oxide micro-powder and its preparation method which comprises, charging bismuth nitrate solution containing 100-350g/L of Bi 3+ into ammonium hydrogen carbonate solution with concentration of 10-25 wt%, controlling the weight ratio of charged ammonium and bismuth between 1.5-3.5, producing bismuth carbonate precipitate while agitating at normal temperature, filtering and washing, carrying out thermal treatment for the filter cake at 100-700 deg. C, thus obtaining the bismuth oxide product, dispersing agent 0.1-5 wt% of the ammonium hydrogen carbonate solution can be charged.