The invention discloses a method for preparing small-particle size large-bulk cobalt carbonate. The method comprises the following steps: heating an ammonium carbonate base solution of certain concentration; respectively adding soluble cobalt salt and ammonium carbonate into the ammonium carbonate base solution according to certain velocities while stirring to react so as to obtain crystal slurry of cobalt carbonate after a certain time of the reaction; and by taking the crystal slurry of cobalt carbonate as a base solution, adding cobalt salt and ammonium carbonate to react for a certain time, thereby obtaining the target cobalt carbonate. The cobalt carbonate prepared by using the method has the characteristics of being small in particle size and large in bulk density.