Abstract: The flue gas condensation technology can recover waste water and heat from wet flue gas and simultaneous reduce the emission of SO₃ acid mist. The numerical models of flue gas condensation, particle movement and particle condensation growth are established to simulate the condensation growth and removal characteristics of SO₃ acid mist in the process of flue gas condensation. The effects of key influencing parameters are analyzed, and the mechanisms of growth and removal are discussed. The results indicate that the SO₃ acid mist has a bimodal distribution at the outlet of the heat exchanger after condensation growth and the highest concentration is in the micron range. The capture mechanisms of acid mist with a sub-micron particle size are mainly thermophoresis and diffusiophoresis. Increasing the inlet flue gas temperature and relative humidity, and reducing tube wall temperature and inlet flow velocity are all conducive to the growth and removal of acid mist. The capture mechanisms of acid mist with micron particle size are mainly inertial collision and interception, and increasing the inlet flow velocity is beneficial for its removal.