Abstract: The Beijing City Atmospheric Pollution Observation Field Experiment (BECAPEX) was deployed during 2001-2003 to obtain the 3-dimensions structure integrate images of Beijing atmospheric dynamic and chemical process. Research on the integrated observations show the thermal dynamic structure of city area is a non-uni-form secondary heat island with a secondary circulation, which affects the distribution of the local pollutants. The data revealed the existence of an air dome (a dome-shape boundary layer) around urban Beijing and provided a comprehensive set of parameters that defined the characteristics of the air dome. Important findings of this study include the synchronous charact eristics of the life cycle of pollutants within the urban atmospheric boundary layer and obvious diurnal variation of pollutants in the boundary layer or under the air dome. In fact, the data reveal that the air dome acts like a large canopy covering the city of Beijing. This phenomenon is closely associated with the temperature inversion and the vertical structure of the boundary layer. Moreover, the diffusion and distribution of air pollutants are related to the multiscale interaction among largescale circulation, mountain and valley wind, and urban heat island circulation. As a result, air pollution in Beijing usually come from local sources, but the sources in the vicinity also have prominent influence.