The green space of Luojiagang Greenbelt Park in Wuhan and its surrounding built environment were used to study the mechanism and effect of urban greenbelts on reducing particulate matter in the air. Three days with clear and windless weather and similar meteorological conditions in winter were repeatedly observed. A combination of land use regression （LUR） model and principal component analysis （PCA） was used to analyze the effect of urban greenbelt on mitigating the concentration of PM₁₀ and PM_2.5 in the air in winter and identify the key influencing factors. The results showed that there was a width effect of urban greenbelt on mitigating the PM₁₀ and PM_2.5 in the air in winter based on the LUR model. The green space with a width of 30-40 meters had the most significant mitigation efficiency of PM₁₀ in the air in winter. In winter， the concentration of PM₁₀ and PM_2.5 in the air inside urban greenbelt was higher than that in adjacent road locations. There was a significant accumulation effect of PM₁₀ and PM_2.5 in the air in urban greenbelt. It is indicated that the effect of urban greenbelt on mitigating the PM₁₀ and PM_2.5 in the air was disturbed by emissions of surrounding traffic pollution. The micro-meteorological conditions created by green spaces of different widths can have a certain impact on the concentration of PM₁₀ and PM_2.5 in the air.