Chlorine (Cl) radicals strongly affect atmospheric oxidation and  the fate of pollutants. Despite several observations, the potential  impacts of nitrogen chemistry associated with NO₂ on Cl  chemistry are poorly understood. Here, we provided direct field evidence  that the nitrogen chemistry enhancements triggered by the increased NO₂ drove daytime nitrate (NO₃^-) photolysis and nighttime NO₃-N₂O₅ reactions, significantly promoting the increases in the concentrations of ClNO₂ and Cl₂ after the Chinese Spring Festival. The enhancement in the Cl chemistry facilitated the elevations of both O₃  and atmospheric oxidation capacity during the winter daytime. Our  findings highlighted the importance of nitrogen chemistry induced by the  increased NO₂ in enhanced Cl chemistry.