This research diagnoses the exposure of the residential population and the vulnerable groups of children and elderly people to air particle pollution in urban Beijing. We surveyed the air particle pollutant concentrations in the field. We used a universal kriging model in a geographic information system to interpolate the spatial distributions of each pollutant. Spatial patterns of air particle pollution were overlaid to community-level population distributions to identify the community exposures to high air particle pollution. Spatial and statistic modeling reveals that high concentration of ultra-fine air particles of particulate matter (PM) 0.3 m is strongly associated with high-population urban communities in the southwest and central western areas in the winter season. By contrast, all the other particle sizes surveyed (PMs of 0.5, 1.0, 3.0, and 5.0 m) indicate that high concentrations in the summer are associated with high-population communities. Reversed spatial and temporal patterns between PM 0.3 m and other particle sizes suggest that PM 0.3 m may have different sources of origin.