In order to understand the blocking effects of forest belts on particulates, the concentrations of particulate matters (PM₁₀ and PM_2.5) in different forest belts near the ecological corridor in southern Beijing Olympic Forest Park adjacent to the southern side of North Fifth Ring Road were observed in May 2013, and major meteorological data such as temperature and relative humidity were collected simultaneously. Results showed that the change pattern of PM₁₀ was consistent with that of PM_2.5, being highest in the morning (7:00 am) and lowest at about 17:00 pm. The forest belts could reduce the concentration of PM₁₀, but the blocking effect was complicated for the PM_2.5. The PM_2.5 concentrations decreased in the elm forest belt and mixed forest belt, but the situation was opposite for poplar forest belt. Particle concentrations in the forest changed with the meteorological factors. PM₁₀ and PM_2.5 concentrations were negatively correlated with temperature. Increased temperature intensified the atmospheric vertical convection, being conducive to the particle diffusion and thus decreasing the particle concentration. Concentrations of PM₁₀ and PM_2.5 had positive relationships with the relative humidity.