This paper performs Large-eddy simulation (LES) of gaseous dispersion in the atmospheric convective boundary layer (CBL) which is capped by a temperature inversion. The vertical temperature flux profile becomes negative within the capping inversion, and its negative peak value is indicated due to the entrainment of a plume and its resulting fluctuation behavior. Turbulence structures based on the entrainment are determined by the strength of capping inversion. Furthermore, gaseous dispersion behavior is sensitively influenced by temperature profile. Our objective is to compare LES results with wind tunnel and observation data for numerical validation, also to investigate characteristics of turbulence structures and gaseous dispersion in CBL with the capping inversion.