Based on field observation and remote sensing data, this research investigated the function of wetlands in reducing the concentration of atmospheric fine particles PM_2.5 in Beijing. The results indicated that wetlands could reduce the PM_2.5 concentration significantly. For example, the concentration of PM_2.5 around Cuihu Lake wetland (P<0.05) was remarkably lower than that nearby bare land. Wetland reduced PM_2.5 in surrounding air by 17% averagely, and the peak reduction could reach 50%. The results also demonstrated the reduction effect of lake and reservoir was larger than that of river (P<0.05). The distribution of PM_2.5 in Beijing showed a spatial pattern of northwest < southeast and suburb region < downtown. It is necessary to appropriately select wetland types especially lake and reservoir wetlands and properly allocate plants in wetlands in future wetland construction, so that wetlands can play roles in humidifying and changing the flow field, thus achieving the goals of improving meteorological conditions, reducing atmospheric fine particles, and relieving haze in urban area. This research provides scientific guidance for wetlands conservation, planning and distribution in Beijing, as well as for making policies of PM_2.5 pollution control.