Spherical calcium carbonate（calcite） crystals were prepared by co precipitation method with boric acid as control agent，calcium chloride and sodium carbonate as raw materials.The effects of the concentration of control agent，reaction tem perature，reaction time and reactant concentration on the particle size and morphology of calcium carbonate were investigated. Results showed that when the concentration of boric acid was 0.4 mol/L，the concentration of calcium chloride was 0.1 mol/L，the dropping rate of saturated sodium carbonate solution at 20 ℃ was 4.9 mL/min，the reaction time was 60 min，the aging time was 60 min，the reaction temperature was 50 ℃ and the amount of substance ratio of calcium chloride to sodium carbo nate was 1∶1，the prepared spherical calcium carbonate particles were uniform in size and the average particle size was 1.57 μm.