Sulfate (SO42-) is one of the most important particulate inorganic components in the atmosphere. Sulfate can directly impact on the solar radiative balance and indirectly as cloud condensation nuclei. Sulfate can alter the physicochemical properties of aerosols in terms of hygroscopicity, acidity, and reactivity.Sulfate is found to be a key composition in particulate matter (PM) during severe haze events in China. In our study, we found photosensitized oxidation of Sulfur dioxide could be a potential important sulfate source for Chinese haze.