Abstract: The atmospheric part of key project from the National Fundamental Research Planning is introduced, i.e., "Air, Water and Soil Environmental Pollution Mechanism and Its Regulating-Controlling Principles in Beijing and Its Ambient Area". Beijing City Air Pollution Observation Experiment (BECAPEX) is the most comprehensive field program carried out to date to characterize the air pollution sources and processes in and around Beijing City during the period from 2001 to 2003. A key issue of the BECAPEX experiment addresses is whether the air quality in the Beijing Metropolitan area (BMA) can meet the standards in 2008 set by the Beijing Olympic Organizing Committee by controlling the emissions within BMA. Observations from BECAPEX reveals that the air quality in BMA is a regional problem. Although the reduction of emissions within BMA can generally improve its air quality, under certain weather conditions, the transports by local heat island circulation, synoptic and large-scale winds can carry pollutants from neighboring regions to the south and east of the BMA. These multi-scale transports play a crucial role in determining the air quality in the BMA. Thus, in order to properly address its air pollution issue, Beijing and its neighboring regions must be considered as an integrated system, where pollution control strategies must be formulated synergistically. Results show that there exists significant difference in the contribution of winter/summer different pollution emission sources to the component character of atmospheric pollution. Surface layer atmospheric dynamic and thermal structures and various pollutant species at the upper boundary of buildings ensembling at urban different observational sites of Beijing in winter and summer show an "in-phase" variation and the spatial scale feature of "influence domain". The power spectrum analysis (PSA) shows that the period spectrum of winter/summer particle concentration accords with those of atmospheric wind field. It is found that from analyzing the urban area thermal heterogeneity, the multi-scale effect of Beijing region urban heat island (UHI) is associated with the heterogeneous expansion of the tall buildings area. In the urban atmospheric dynamical and thermal characteristic spatial structures, the turbulent scale feature of the urban boundary layer (UBL) of architectural complexes has an important impact on the multi-scale feature of the urban atmospheric pollution. The comprehensive analyses of the variational analysis field of Moderate Resolution Imaging Spectroradiometer (MODIS) AOD-surface PM10 under the condition of clear sky and the correlation resultant wind vector field for pollution sourcetracing suggest that the emission sources for winter Beijing atmospheric pollution aerosols particle might be remotely traced to the south peripheral greater-scale spatial range of Hebei, Shandong, and Tianjin etc. The backward trajectory feature of winter/summer air particles exhibits analogous multi-scale feature, and depicts the difference in the scale feature of the pollution sources spatial distribution in different season. The peripheral source trajectory paths of urban atmospheric pollution (UAP) mainly come from the fixed industrial surface source or heating surface source in the outskirt of Beijing. The high value area of the winter Total Ozone Mapping Spectrometer (TOMS) AOD lays in the Beijing region and its south peripheral area, an S-N zonal pattern, which reflects the dynamical effect of peripheral topographic pattern on the diffusion of regional scale atmospheric pollution sources. Study suggests that the extent of winter atmospheric pollution within the "valley" megarelief in Beijing and its periphery is closely related to the pollution emission sources of the south peripheral area; and the significant "anti-phase" variation feature of the winter AOD and sunshine duration in Beijing and its peripheral areas, and the regional scale correlation of low cloud cover, fog days, and aerosols reflect the local climatic effect of aerosol influence in this region. Based on the analysis of the air pollution observational data, several models developed by members of this program are revealed.