The invention discloses a preparation method for rice-grain-shaped light calcium carbonate. The preparation method comprises the following steps: calcining lime stones with natural gas, adding digesting water to complete digesting reaction, performing screening, impurity-removal and ageing, adding a crystal form controller, introducing lime kiln kiln-gas to perform carbonization, pumping into a homogenizing tank to perform re-aging, and introducing purified, cooled and compressed lime kiln kiln-gas to perform secondary carbonation reaction, thereby preparing calcium carbonate slurry; and adding a modifying agent into the calcium carbonate slurry and stirring, and performing filter-pressing and dehydrating, drying, crushing and grading, thereby obtaining the rice-grain-shaped light calciumcarbonate. The light calcium carbonate crystal form prepared by the preparation method is rice-grain-shaped, has a long diameter of 150-200 nm, a short diameter of 30-50 nm, a BET specific surface area of 20-22 m<2>/g, a small length-diameter ratio, a high specific surface area and good dispersion, and can be used for manufacturing food and cosmetics; and moreover, the process is simple and feasible, the cost is low, the price is low, and the economic benefits are relatively good.