Heterogeneous oxidation of SO2 by NO2 on aerosol particles has recently been thought as one of the major formation pathways of sulfate in the polluted troposphere, but the underlying chemical mechanisms and kinetics remain uncertain. Here, we show that sulfate formation via NO2 oxidation is critically dependent on the charges at the air-aqueous interface by combining lab experiments, theoretical chemistry calculations, and atmospheric measurements. Our results reveal that the oxidation rate (k_(〖NO〗_2+〖HSO〗_3^- )) (2.1x108–7.0x109 M-1s-1) of SO2 by NO2 in the aerosol aqueous phase in Chinese haze periods is 3–4 orders of magnitude larger than the traditionally held value for the bulk phase due to the accumulation of chloride and carboxylic anions at the air-aqueous interface, which significantly accelerates the SO2 oxidation by enhancing the uptake of NO2 through interfacial electrostatic attraction. Atmospheric models not accounting for this aerosol interfacial process likely produce major misrepresentations of tropospheric sulfate aerosols under polluted conditions.