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Street dust is a vital pertinent indicator to urban environmental quality, while only limited information is available on Hg from street dust in a subtropical city, as well as the bonding reactions between Hg and dust. In the proposed research, the physical properties of street dust collected from a subtropical city (Nanning) were analyzed with FT-IR and XRD; it was proved that the dust was mainly composed by quartz and calcite. The concentration of Hg was 338.11 ± 222.04 μg/kg (SD, n = 30), which was consistent with that in some mega-cities in China. Although Hazard Quotient values for Hg indicated non-carcinogenic health risk to humans, Hg pollution level of dust in Nanning was assessed to be moderate-heavy based on high Igeo and Er, which still needs public concerns. The anthropogenic source could be exhaust gas discharged from traffic vehicles, industrial and hospital activities, while tremendous amount of non-motor vehicles driving back and forth in the city, which re-suspended fine particles to concentrate Hg in the air. The results of XPS analysis further revealed that Hg combined with halogen, organic matter and S, or was adsorbed on the surface of the street dust. [ABSTRACT FROM AUTHOR]