Nano-sized calcium carbonate, as a multifunctional material, is widely used in various industrial fields. The morphology, particle size, surface property of CaCO3 particles have great impact on the application effect. This study presents an energy-saving and efficient approach to controllably prepare CaCO3 nanoparticles and conduct surface modification simultaneously. Ca(OH)(2)/CO2 carbonation method was adopted to prepare CaCO3 nanoparticles using a membrane dispersion microreactor in the presence of calcium stearate (CaSt(2)) surfactant. The effects of gas and liquid flow rates, temperature and the dosage of surfactant were systematically investigated. The effect of surface modification was evaluated by contact angle and active ratio. The as-prepared hydrophobic CaCO3 nanoparticles were of good dispersity, with an average particle size of 34 nm, a specific surface area of above 30 m(2)/g and a contact angle of 107.8 degrees. In this work, the effect of surfactant on the carbonation reaction was greatly diminished by adding CaSt(2) surfactant to a portion of Ca(OH)(2) slurry. Additionally, the modification process was carried out without organic solvents and high temperature. As compared to post-modification method, the in-situ modification process is of significant practical importance because of high production efficiency, excellent process stability, and high product quality. (C) 2019 Published by Elsevier B.V.