The non-hydrostatic mesoscale model MM5V3 is used to simulate the wind and temperature fields of the atmospheric boundary layer over Beijing area in summer with the mesh resolution of 1 km. The simulation results show that the numerical model can successfully simulate the urban heat island effect and the wind and temperature fields which are affected by the complicated topography and urban heat island. The results show that: (1) the west area (from Haidiau to Fengtai Districts) is always the high temperature center of Beijing, where the surface temperature is about 6 K higher than the other suburbs; and (2) due to the unique topography the wind of Beijing area during the daytime is southern anabatic wind and at the night is northern katabatic wind. The results comparing well with the data from surface observation stations validate the accuracy of the simulation.