The present paper investigates the simultaneous removal and synergistic effect of SO2 and NOx in natrium-alkali solutions in a countercurrent packed column in continuous flow mode. On the basis of high SO2 removal effciency, the NOx removal effciencies under different process variables such as natrium-alkali concentration, reaction temperature, initial pH value, SO2 concentration, oxidation degree of NOx and additive were investigated. The reaction mechanism for synergistic effect and simultaneous removal of SO2 and NOx based on the natrium-alkali method were deduced. The removal effciency of SO2 was about 100%, but the effect mechanism of denitration effciency was complex. In this paper, the optimal conditions for simultaneous removal of SO2 and NOx were determined. The experimental results showed that the simultaneous desulfurization and denitration was possible, and the removal effciencies could meet the increasingly stringent emissions regulations of IMO.