MgO slurry become more and more important in wet desulfurization process because of high desulfurization activity and recyclable by-products. While the removal of SO2 by micron-sized MgO slurry is limited due to particle size. Hence, micro-sized MgO slurry and MgO nanofluids of the same concentration were prepared. The stability of MgO nanofluids had been investigated. The density and viscosity of MgO nanofluids increased with the increase of concentration, but decreased as the temperature increase, and MgO nanofluids belong to Newtonian fluids. The evaluation of desulfurization effect and calculation of the mass transfer coefficient indicated that MgO nanofluids had better desulfurization effect compared with MgO slurry. The desulfurization efficiency increased with the increase of concentration, while the growth rate of desulfurization efficiency dropped sharply as the concentration exceed 4 wt%. Therefore, reducing the particle size properly can improve desulfurization efficiency of MgO absorbent in removal of SO2 from flue gas. (C) 2020 Elsevier B.V. All rights reserved.