The role of particulate matter (PM) in causing adverse health effects on the human body has been confirmed by many studies, because its redox components may cause in situ production of excessive reactive oxygen species (ROS) in the human body. The capacity of PM to deplete antioxidants and generate ROS is defined as oxidative potential (OP). However, few studies have explored on the OP of PM in different regions of China, especially in atmospheric background regions. In order to explore the OP of water-soluble components of PM in the background area of the Yangtze River Delta, we collected PM_2.5 and PM₁ in Lin’an in winter and summer. The OP of PM in Lin’an was analyzed by dithiothreitol (DTT) and ascorbic acid (AA) analysis, and the contribution of long-distance air mass transmission to the OP of PM in the area was analyzed by backward trajectory. This study showed that the OP of PM in Lin’an was still at a relatively high value of exposure (summer, OP^DTTv, 0.71 ± 0.25 nmol∙min⁻¹∙m⁻³, OP^AAv, 0.37 ± 0.29 nmol∙min⁻¹∙m⁻³; winter, OP^DTTv, 1.24 ± 0.33 nmol∙min⁻¹∙m⁻³, OP^AAv, 0.32 ± 0.40 nmol∙min⁻¹∙m⁻³) and PM₁ in Lin’an contributed a lot to the OP of PM_2.5, all above 60%. There were significant seasonal variations in the OP of PM, OP^DTTv was higher in winter, as it was relevant to the high mass concentration of PM, while OP^AAv was slightly higher in summer, as it was affected by photochemical reactions in summer. Local emissions contributed more in summer, and long-distance transportation from other regions contributed more in winter. Therefore, we suggest paying more attention to the impact of PM₁ on health effects, controlling local emissions in summer and controlling the input of external sources to reduce the mass concentration of PM in winter and adverse health effects of PM.