Influence of land surfaces on the pollen dispersal under urban environment is rarely investigated. We measured pollen concentration dispersed from four commonly used urban tree species (Pinus tabulaeformis, Magnolia denudata, Pinus bungeana and Ailanthus altissima) on two spring windless sunny days in 2006 in Beijing. The pollen concentration and microclimate measurements were conducted in the locations 10m away from the sampling trees at 1.5m above the ground. Our objectives were to contrast the impact of grass covered (Soft) and paved (Hard) surfaces on the diurnal variations of pollen disposal. Our research indicated that: (1) Diurnal variations of pollen dispersal among four species had similar tendency in same urban surface condition. But the same tree species showed distinctive diurnal variations under different surface conditions (soft and hard). Under soft ground, diurnal variation of tree pollen had one peak presented at 14:00pm while the lowest pollen concentration was at 04:00am. That was positively correlated with air temperature but had negative correlations with relative humidity. The diurnal patterns of tree pollen showed clear variation with high peaks at around 14:00pm and 20:00pm and low values around 04:00am and 18:00pm under hard ground. And the peak of pollen concentration appeared at 20:00pm was consistent with the peak of ground temperature in hard ground. Overall, the pollen concentration during the day was significantly higher than at night while the pollen concentration under hard ground was significantly higher than under soft ground during the night. (2) Peak pollen concentration at 20:00pm under hard ground could be attributable to the thermal dynamics of the ground. Heat strapped by hard ground during the daytime was released at night, causing the convection movement of air near the ground and promoting tree pollen release into the atmosphere. Consequently, the pollen concentration peak happened at night. (3) Pollen dispersal during the daytime was not significantly affected by different surface conditions. However, the surface impacts on the pollen dispersal were observed during the night. Comparing with soft ground, hard ground showed greater and longer influence on pollen dispersing in the air. That made the pollen concentration remained at high concentration level for several hours in the near ground air after the sunset. This phenomenon will lead to the extended time of allergenic pollen dispersal and aggravated pollen pollution. Therefore, urban forest tree species selection and urban surface mulching were recommended to avoid possible pollen pollution for urban dwellers, and most importantly for those pollen allergy-pro citizens. In addition, we recommended that the hay fever patients should avoid their outdoor activities and sports during the time when the pollen concentration is high. This would lead to lower the risks of allergenic pollen threats to their health.