Abstract: Using manganous sulfate （MnSO<SUB>4</SUB>） as raw material,ammonium hydrogen carbonate （NH<SUB>4</SUB>HCO<SUB>3</SUB>） as precipitating agent and sodium dodecyl sulfate as particle size controller and through the process of quick addition of MnSO<SUB>4</SUB> and NH<SUB>4</SUB>HCO<SUB>3</SUB> solutions at same time,monodisperse submicron manganous carbonate （MnCO<SUB>3</SUB>） spherical particles were prepared by controlling suitable reaction crystallization conditions.Effects of reaction crystallization conditions on particle size and morphology of MnCO<SUB>3</SUB> were researched by means of scanning electron microscopy （SEM）,X-ray powder diffraction （XRD）,and particle size analyzer etc..Results showed that monodisperse spherical manganous carbonate fine particle with average particle size of 540 nm when concentrations of MnSO4 and NH<SUB>4</SUB>HCO<SUB>3 </SUB>are 1.2 mol/L and 0.7 mol/L respectively,reaction temperature is 30 ℃,reaction time is 30 min,and amount-of-substance ratio of NH<SUB>4</SUB>HCO<SUB>3</SUB>to MnSO<SUB>4</SUB> is 1.5∶1.