The invention provides a method for spray carbonation of nanometer calcium carbonate in order to solve the problems of uneven particle size distribution, low production efficiency and high device costin existing spray carbonation technologies. The method comprises the following operating steps: a calcium hydroxide slurry is pumped into a spray carbonizer, a reducing portion is arranged in the spray carbonizer, and the calcium hydroxide slurry and a carbon dioxide gas sucked by a negative pressure generated by the reducing portion are mixed at a high speed; and the obtained gas-liquid mixtureformed by the spray carbonizer is introduced into a bubbling tank by an extension tube, the extension tube is inserted to a position below the liquid level in the bubbling tank, and the unreacted carbon dioxide gas is bubbled in the bubbling tank. The invention also discloses a system for spray carbonation of nanometer calcium carbonate. The method for spray carbonation of nanometer calcium carbonate ensures the dimensional consistency of the nanometer calcium carbonate, reduce the proportion of particles with too large or too small particle sizes and improves the production efficiency.