Snow with high albedo enhances atmospheric photochemical reactions, influencing key oxidative processes. Nitryl chloride (ClNO<sub>2</sub>), as a strong oxidizing species, is generated by the heterogeneous reaction between dinitrogen pentoxide (N<sub>2</sub>O<sub>5</sub>) and chloride adsorbed on aerosol and the ground surfaces. After sunrise, the photolysis of ClNO<sub>2</sub> rapidly releases highly reactive chlorine radicals (Cl·), which contributes to the formation of secondary pollutants. However, the pollution mechanisms in high-latitude, snow-covered regions associated with increased chlorine emissions remain unclear. In this study, we employed the WRF-CAMx model (Weather Research and Forecasting Model-Comprehensive Air Quality Model with extensions) with a modified chemical mechanism (CB6r2h_lts, Carbon Bond 6 revision 2 with heterogeneous chemistry for low-temperature and snow-covered conditions) that incorporated heterogeneous N<sub>2</sub>O<sub>5 </sub>reactions and ClNO<sub>2</sub> photolysis on ground surfaces to assess their impact on regional atmosphere under snow-covered conditions in Northeast China. Our findings reveal that under snow-covered conditions, the YU20 aerosol scheme (from study by YU et al., 2020) outperforms the BT09 scheme (from study by Bertram et al., 2009) in simulating N<sub>2</sub>O<sub>5</sub> and ClNO<sub>2</sub> concentrations within the CAMx model. Incorporating anthropogenic chlorine emissions and ground surface chemistry significantly improved model performance for ClNO<sub>2</sub>, reducing the mean bias (MB) from -105.78 pptv to 2.66 pptv and increasing the index of agreement (IOA) from 0.39 to 0.86. These processes resulted in a maximum hourly increase of 3.65 µg/m³ in PM<sub>2.5</sub> (relative contribution: 15.34 %) and 3.41 ppbv in MDA8 O<sub>3</sub> (5.68 %). Notably, ground surface chemical processes were identified as the dominant source of nocturnal ClNO<sub>2</sub>, contributing approximately 28.36 % to nighttime accumulation across Northeast China. These findings not only highlight the pivotal role of chlorine chemistry in atmospheric processes under snow-covered conditions, but also provide crucial support for the refinement of the mechanisms governing the flux exchange of chemical substances between the atmosphere and the cryosphere.