The invention discloses an environment-friendly nano 
calcium carbonate carbonation method which comprises the following steps: S1, injecting 
lime slurry into a reaction kettle, stopping feeding when the feeding amount is 1 / 5-2 / 5 of the volume of the reaction kettle, and adjusting the rotating speed at the same time; introducing 
kiln gas into the reaction kettle, and discharging reaction 
tail gas 
after treatment; when the pH value of the 
slurry in the reaction kettle is 7.5-8.0, stopping air intake, and adjusting the rotating speed; and s2, injecting 
lime slurry into the reaction kettle containing the 
seed crystal, stopping feeding when the feeding amount reaches 4 / 5 of the volume of the reaction kettle, adjusting the rotating speed, stirring and aging; and introducing the 
kiln gas again, and when the pH value of the slurry in the reaction kettle is 7 and the slurry at the upper part and the lower part in the reaction kettle has no relative 
temperature difference, enabling the 
carbonation reaction to reach the end point. According to the method, the nano 
calcium carbonate with the average particle size of 40-100 nm is stably produced, and meanwhile, in the production process, the generated 
tail gas is treated and then discharged, so that the 
atmosphere is hardly influenced, and the 
environmental protection requirement is met.