To comprehensively investigate and quantify the impact of urban vegetation on regional meteorological conditions and its seasonal variation tendency, series of sensitive cases are designed with the adoption of the RBLM model and using the Suzhou city, China, as a case study. The results indicate that:urban vegetation would contribute to a reduction of air temperature and urban heat island intensity (UHⅡ), and this effect would be amplified with the increase of vegetation coverage. Modeled daily mean UHⅡ reaches 1.8, 1.4 and 1.0℃ under tree coverage of 0, 20% and 40%, respectively. Compared to the real distribution patterns of vegetation in Suzhou, the ideal greenery scenarios with tree coverage of 20% and 40% could lead to a reduction of 0.23 and 0.84℃ in daily mean air temperature. Urban vegetation may also increase the canopy humidity through the evaporation and transpiration effect on leaf and ground surfaces. By increasing tree coverage from 0 to 20%, and then to 40%, the specific humidity at noontime is 2.46, 2.61 and 2.78 g kg^-1. Tree planting is generally more notable in modifying ambient temperature and humidity than grass surfacing with the same coverage. Trees could also affect the surface energy balance by reducing the amount of solar radiation that reaches the ground surface, hence reducing the surface temperature. The surface net radiation flux at noon is 433, 382 and 332 W m^-2 when the tree coverage is 0, 20% and 40%, respectively. In addition to the reduction of surface temperature, the evaporation and transpiration effect of vegetation would contribute to the decrease of sensitive heat flux as well as increase of latent heat flux. The meteorological effect of urban vegetation is more notable in summer than in winter.