Building's effect is developed in Regional Boundary Layer Model.The simulated results illustrate that it can simulated the effect of buildings on urban air flow field.According to the urban morphology,we design the different building heights and densities.The simulated results show that the buildings can weaken the wind speed in urban area and lead to convergence in lower layer atmosphere.The weaken can reach a peak of 1.6 m/s.The dynamic production of turbulence is strengthened and the turbulence transportation is greater.The presence of building leads to a more instable stratification with a mixing layer.The top of boundary layer can improved.It leads to a weaker energy exchange between atmosphere and the earth.In daytime the heat exchange between atmosphere and the earth is weakened while strengthened at night.All of the simulations illustrate that the buildings play an important role in urban air flow field and boundary layer structure,particularly when wind speed is great.