Wall function is preferred to model the low Reynolds-number flow near wall based on the Reynolds-averaged Navier-Stokes turbulent models. Wall function problem in simulating the atmospheric boundary layer based on the standard turbulent model was investigated in this paper. An extra term which considers the extra effects induced by non-uniform and irregular distribution of roughness elements such as various structures on the land surface was proposed and appended to the widely accepted standard wall function. The effectiveness and application situation of the proposed term was firstly demonstrated by simulating a neutral wind field with the scale of 1:300 featured by larger aerodynamic roughness length. The flow around the TTU model in a neutral wind field with the scale of 1:50 was then simulated. The extra term is shown to be necessary to solve the wall function problem by preserving the inlet flow boundary conditions in both cases.