Abstract: Green space plays an important role in reducing PM_2.5, since it can efficiently absorb suspended particles in the air. A quantificational method of dust detention service of green space was proposed in this study, based on the mechanism of PM_2.5 reduction by plant. Daily, summer, winter and whole year cumulative dust amounts reduced by green space with different landscape types of Haidian District, Beijing, were quantified. The results showed that both of dust reduction frequency and daily cumulative dust amount in winter were considerably lower than those in summer. Mountain woodlands in the west of Haidian District provided the highest average PM_2.5 reduction service, and the fragmented agricultural and forest landscapes in the northern plains provided the highest total dust detention service, while the southern area had the lowest dust detention service except for several parks. PM_2.5 detention service model was very useful to quickly quantify how much dust could be reduced by green space and where were these services, which was very important for the development of urban green space and improvement of air quality.