The invention discloses a spherical calcium carbonate and a preparation method thereof. The preparation method comprises following steps: mixing quicklime with water according to a ratio, carrying outdigestion and aging, then sieving the solution to remove impurities, adding ethanol into the slurry, carrying out refining and regulating to obtain calcium hydroxide slurry; transferring the preparedslurry to a super gravity reactor, adding a crystal form controller, controlling the carbonization temperature, CO2 gas flow, and super gravity level to carry out countercurrent contact between the calcium hydroxide slurry and CO2 gas to trigger carbonization reactions; after carbonization, carrying out centrifugation, drying obtained precipitates, and grinding to obtain spherical calcium carbonate. Calcium hydroxide is taken as the raw material, alcohol and water are taken as the solvents, the cost is low, the spherical calcium carbonate is prepared in a super gravity field by a carbonization method, the microscopic mixing and mass transfer process are greatly enhanced, the carbonization time is short, the production efficiency is high, the particle size distribution range is narrow, theparticle size is small, the morphology is uniform, the dispersing property is good, and the spherical calcium carbonate is suitable for industrial application.