In order to learn the influences of urban buildings on the surrounding wind fields, the wind fields of different types of buildings with the large-eddy simulation were simulated and the wind fields with various ventilation indexes were quantitatively assessed. Results show that PALM (Parallelized LES Model) can basically reflect the structures of the wind fields. Wind fields are affected by the building height, height variance and initial flow. The flow attenuation is mainly reflected in the horizontal component, especially when the average height is higher or with larger height variance and irregular distribution, the horizontal wind field would attenuate more with ventilation effect becoming worse. Meanwhile, the vertical velocity component w increases, so that the air exchange rate in the vertical direction would be larger. The initial flow does not affect the wind profile in shape, when the wind speed in lower height and the overall air exchange rate are proportional to the initial flow.