Abstract: Flow and temperature structures in Shenyang City,Liaoning Province have been analysed according to the fields experiments carried out in December,1984.Features of wintertime urban boundary layer are obtained.As surface wind is light the effects of urban heat island are best expressed.There are flow convergence and ascending in the lower part of boundary layer.Return flow may occur in the downwind suburb.While wind is strong the friction effect of urban dominates.Convergence and ascending occur in the upwind part of the city,while divergence and decending in the downwind part.The wind retardation by friction may extend to a few hundred meters.During nighttime with light wind the depth of ground inversion is about 200m.The depth of internal boundary layer increases with the distance from the upwind hedge to about 100m at the downwind fringe.In the daytime with light wind heavy pollution may cause cool island and retard the development of convective boundary layer.