Abstract: Limestone is the main raw material of preparing nano-sized calcium carbonate.Quality of limestone and calcined limestone can affect the quality of nano-sized calcium carbonate seriously.In order to deeply analyze the effect of calcined temperature on the process of nano-sized calcium carbonate production,effect of calcination on all kind of technical parameters of slaked reaction and of carbonation reaction was analyzed by testing of limestone calcined at different temperature.Results showed that: 1) If the calcining temperature of limestone is too high or the time is too long,it will effect lime′s activity,besides,it will make some different effects on the viscosity of calcium hydroxide emulsion and the particle formation of carbonation reaction.2)If the temperature is too low,limestone can not be calcined completely,then it can not be used fully and it is not good for economic benefit of the company.