Heterogeneous uptake of dinitrogen pentoxide (N 2 O 5 ) and production of nitryl chloride (ClNO 2 ) are important nocturnal atmospheric processes that have significant implications for the production of secondary pollutants. However, the understanding of N 2 O 5 uptake processes and ClNO 2 production remains limited, especially in China. This study presents a field investigation of the N 2 O 5 heterogeneous uptake coefficient (γ(N 2 O 5 )) and ClNO 2 production yield (ϕ) in a polluted area of northern China during the summer of 2014. The N 2 O 5 uptake coefficient and ClNO 2 yield were estimated in 10 selected cases using simultaneously measured concentrations of ClNO 2 and particulate nitrate. The determined γ(N 2 O 5 ) and ϕ values varied greatly, with an average of 0.022 for γ(N 2 O 5 ) (in range of 0.006–0.034) and 0.34 for ϕ (range, 0.07–1.04). The variations in γ(N 2 O 5 ) could not be fully explained by the previously derived parameterizations of N 2 O 5 uptake that consider nitrate, chloride, and the organic coating. Heterogeneous uptake of N 2 O 5 was found to have a strong positive dependence on the relative humidity and aerosol water content. This result suggests that the heterogeneous uptake of N 2 O 5 in Wangdu is governed mainly by the amount of water in the aerosol, a phenomenon that differs from other field observations in the United States and Europe. Laboratory-derived parameterization also overestimated the ClNO 2 yield. The observation-derived ϕ showed a decreasing trend with an increasing ratio of acetonitrile to carbon monoxide, an indicator of biomass burning emissions, which suggests a possible suppressive effect on the production yield of ClNO 2 in the plumes influenced by biomass burning in this region. The findings of this study illustrate the need to improve our understanding and to parameterize the key factors for γ(N 2 O 5 ) and ϕ to accurately assess the photochemical and haze pollution.