Sulfur dioxide (SO2) is the main component of air pollution. Recently, sodium lactate (NaLa) aqueous solution (aq) was demonstrated as a highly efficient, renewable, and stable absorbent for SO2 absorption from flue gas. However, sulfuric acid (H2SO4) accumulated during long-term SO2 absorption and desorption cycles. To remove H2SO4 from NaLa (aq) efficiently, a method based on the common-ion effect was proposed in this work. The results indicated that the residual concentration of sulfate anion (SO42-) decreased with decreasing the water content. Residual SO2 in NaLa (aq) did not influence the removal of H2SO4. After the removal, the content of residual SO42- was 0.47 wt % and the removal rate of H2SO4 was 95.6%, with a water content of 34 wt % at 20 degrees C. In comparison to other reported methods, our method to remove H2SO4 in absorbents did not introduce other ions and block the absorption tower. It was noted that the evaporation of water to decrease the water content was combined with the regeneration of NaLa (aq), without any extra evaporation energy. NaLa (aq) was not changed during the removal process. Moreover, the SO2 absorption capacity in H2SO4-removed NaLa (aq) was comparable to the capacity of virgin NaLa (aq), and no obvious change could be found after 5 cycles of H2SO4 removal. The mechanism of removing H2SO4 from NaLa (aq) studied with Fourier transform infrared spectroscopy indicated that H2SO4 was removed in the form of Na2SO4 without crystal water as a result of the common-ion effect. Furthermore, a new process for SO2 absorption with H2SO4 removal from NaLa (aq) was proposed.