Abstract: To address the slow early-stage carbonation rate of hydrated lime, two carbonation accelerators, NaHCO₃ or Na₂CO₃, were mixed into the hydrated lime, and the effects of the molar ratio of CO₃^2- to Ca²⁺ (n(CO₃^2-)∶n(Ca²⁺)) on physical properties, compressive strength and microstructure of hydrated lime were investigated. Results show that increasing n(CO₃^2-)∶n(Ca²⁺) can shorten the initial and final setting time of the hydrated lime paste when the consistency is kept the same, however, the increasing water-lime ratio is not conducive to the water evaporation of hydrated lime moisture and later carbonation. When n(CO₃^2-)∶n(Ca²⁺) is less than 0.18, both carbonation accelerators can reduce capillary water absorption, water absorption and porosity of hydrated lime, while increasing the softening coefficient of hydrated lime. The carbonation accelerators can significantly increase the early compressive strength of hydrated lime, and the 28 d compressive strength of two hydrated lime pastes modified by carbonation accelerator is the highest at n(CO₃^2-)∶n(Ca²⁺) of 0.18, respectively, with increases of 97.73% and 39.77%, compared to the control group. However, n(CO₃^2-)∶n(Ca²⁺) more than 0.18 is not conducive to the later strength development of hydrated lime. According to SEM images, calcite-type CaCO₃ is the main product of hydrated lime carbonation, and the increased n(CO₃^2-)∶n(Ca²⁺) promotes to hydrated lime carbonation. In conclusion, carbonation accelerators containing Na⁺ adversly affect the hydrated lime property, and the internal mixing of carbonation accelerator has a significant upliftment on hydrated lime properties when n(CO₃^2-)∶n(Ca²⁺) is less than 0.18.