To study the difference and the reasons of simulating the Urban Heat Island (UHI) with the Town Energy Balance (TEB) scheme and with the SVAT (soil－vegetation－atmosphere transfer) scheme, some ideal numerical experiments are performed with a regional boundary layer model, which is developed by Nanjing University. Results show that because of the great ability of simulating urban heat storage, the TEB scheme is better than the SVAT scheme in simulating the UHI phenomenon. Moreover, the UHI obviously affects the thermal structure of urban boundary layer, that is, there is obvious difference of surface potential temperature profile between urban and rural areas in the morning and the evening. At the same time, urban temperature is higher than rural temperature all through the day. The reaching height of the temperature difference between urban and rural areas in the daytime is higher than that in the nighttime. The anthropogenic heating and building structure play an important role in the UHI. The effect of anthropogenic heating on the UHI in the nighttime is greater than that in the daytime. As far as the turbulence in the daytime over the urban areas is concerned, the effect of buildings is larger than that of the anthropogenic heating.