Abstract: As understanding of the light absorption of carbonaceous aerosols increases, brown carbon (BrC, i.e., light-absorbing organic carbon), another species of light-absorbing carbon in addition to black carbon (BC), has been highlighted in recent years and has become a new hotspot in the research field of atmospheric environment internationally. However, research on BrC in China is not common until now. Based on existing literature, BrC can be roughly divided into three categories, i.e., tarry materials, humic-like substances (HULIS) and other light-absorbing organic aerosols, and can originate from two pathways, i.e., primary emission and secondary formation. In addition, BrC is in a weakly-bound aggregate morphology because of the shortage of graphitic structure, and is usually highly soluble because of the richness of oxygen content. The optical properties of BrC are often characterized by ngstrm absorption exponent (AAE), mass absorption efficiency (MAE), refractive index (RI) and single scattering albedo (SSA), with a distinctive feature of AAE>1, in contrast to BC (for BC, AAE=1), due to the deficiency of sp² hybrid orbital structure in BrC. Although BrC is by some researchers quantified through methods based on the optical, thermal/optical, chemical and mass-spectrometric principles, there are no widely-accepted standard methods and reference materials for BrC quantification, which makes BrC measurements operationally-dependent. Given that the history of BC emission estimation is longer than that of BrC's, some researchers have tried estimating BrC emissions by referencing concurrently released BC emissions. Future research on BrC is proposed towards BrC's climate effects, formation mechanisms, emission factors, measurement methods and emissions abatement.