To evaluate sampling artifacts of PM2.5 with conventional filtration system (FS), a contrastive study between the FS and a honeycomb denuder system (HDS) in measuring atmospheric concentrations of PM2.5 and its main water-soluble ions (Cl–, NO3–, SO42– and NH4+) was conducted at a urban site in Tianjin, China in both summer and winter. In this study, we confirmed the optimum concentration of absorbents of Na2CO3 and citric acid for HDS were 3% and 6% in summer experiments and 4% and 5% in winter experiments. Daily mean concentrations of Cl– obtained by HDS were higher than those by FS both in summer and winter. In contrast, the HDS gave lower daily mean SO42– concentrations than FS in both summer and winter. For NO3– and NH4+, concentrations obtained by HDS were lower than those obtained by FS in winter. However, the HDS gave larger values of NO3– and NH4+ than FS in summer. The different results of different ions were in response to the concentrations of interfering gases in ambient air and chemical characteristics of ionic species. In addition, the concentrations of PM2.5 obtained by HDS were higher than those obtained by FS in summer, while virtually no significant difference between HDS and FS in winter. Our study points out that investigating optimum concentrations of coating solutions before denuder system sampling is necessary. Moreover, it is essential to make careful evaluation and modiﬁcation when applying FS in highly polluted Environment, especially for PM2.5 ions determining.