Totally 63 samples of size-segregated particulate matter (PM) were collected using an 8-stage Anderson cascade impactor in autumn 2016 at the Xianlin campus, Nanjing University. The concentrations of 24 metal elements were analyzed by the ICP-MS. Size distribution characteristics of mass concentrations, enrichment factors (EFs), and possible sources of different metal elements were studied. Results showed that the size distribution of the mass concentration was bimodal, peaking at 0.4~1.1 and 5.8~9 μm, respectively. With regard to the metal elements, we found three types of size distribution. The first type had a mono peak at coarse size segment (3.3~5.8 μm), including Na, Al, Ca, Mg, Co, Ce, Sr and Ba. The second had a mono peak at fine size segment (0.4~1.1μm), including Zn, As, Cd, Ag, Tl and Pb, and the third had two peaks at fine (1μm) and coarse (5μm), respectively, including K, Se, Li, Be, Mn, V, Cu, Cr, Ni and Fe. According to the value of the EFs, the elements were divided into three groups. They were a slightly enriched group with EFs lower than 5 (Ba, Ca, Ce, Sr, Mg, Fe, Co, Mn, Be and V), a moderately enriched group with EFs between 5 and 100 (Li, Na, Ni, K and Cr), and a highly enriched group with EFs larger than 100 (Cu, Tl, Zn, As, Pb, Ag, Cd and Se). The characteristics of the size distribution and the EFs reflected different sources of atmospheric PM in Nanjing, which were meaningful for further researches on health effects and for policy making for air pollution control.