Abstract: Based on atm ospheric diffusion K-theory with its turbulent exchang ecoefficient as a function of the lagrangian time scale and standard variance of the turbulence in atmosphere,the atmospheric disper sion PDF models are obtained,in which the statistics of wind speed are directly used as its parameters instead of traditional dispersion paraeters.The bi-gaussian PDF is derived,in convective boundary layer (CBL ),from the statistics of vertical velocity in both of the downdrifts and updrif tsregion that are investigated theoret ically in the other part of this paper.In CBL,if its driven parameters such as the convective velocity scale w*,the mixing depth hi and the average wind speed atrelease level were given,the non-dim ensionalizing distribution of the concent ration calculated from the PDF modelgiven here are fairly agree with that given from the measurements in CONDORS experiment or the resulting from numerical simulation.