In this paper, the effect of sodium humate (HA-Na) and seawater on the absorption of SO₂ in flue gas was investigated. At the same time, the effects of the initial pH value of seawater and SO₂ concentration on seawater desulfurization were also evaluated. The experimental results showed that seawater had the ability to absorb SO₂. SO₂ dissolved in seawater can react with HCO₃^– and CO₃^2– plasma to produce CO₂, which can prompt the absorption reaction. Besides, the addition of HA-Na can improve the performance of seawater desulfurization and increase the efficiency of seawater desulfurization. It also prolonged the desulfurization time and improved the problem of high usage amount of seawater in practical applications. With the increase of HA-Na addition, the desulfurization efficiency and the efficient desulfurization time of seawater increased. The efficiency of seawater desulfurization decreased with the initial pH value of seawater. The greater the concentration of SO₂, the faster the absorption efficiency of SO₂ by the solution decreased and the shorter the time for the solution to reach saturation.