Anthropogenic emissions of Black carbon (BC) aerosol are transported from Southeast Asia to the southwestern Tibetan Plateau (TP) during the pre-monsoon; however, the quantities of BC from different anthropogenic sources and the transport mechanisms are still not well constrained because there have been no high-time-resolution BC source apportionments. Intensive measurements were taken in a transport channel for pollutants from Southeast Asia to the southeastern margin of TP during the pre-monsoon to investigate the influences of fossil fuels and biomass burning on BC. A receptor model coupled multi-wavelength absorption with aerosol species concentrations was used to retrieve site-specific Ångström exponents (AAE) and mass absorption cross-sections (MAC) for BC. An ‘aethalometer model’ that used those values showed that biomass burning had a larger contribution to BC mass than fossil fuels (BCbiomass = 57% versus BCfossil = 43%). The potential source contribution function indicated that BCbiomass was transported to the site from northeastern India and northern Burma, The Weather Research and Forecasting model coupled with chemistry (WRF-Chem) model indicated that 40% of BCbiomass originated from Southeast Asia, while the high BCfossil was transported from the southwest of sampling site. A radiative transfer model indicated that the average atmospheric direct radiative effects (DRE) of BC was +4.6 ± 2.4 W m-2 with +2.5 ± 1.8 W m-2 from BCbiomass and +2.1 ± 0.9 W m-2 from BCfossil. The DRE of BCbiomass and BCfossil produced heating rates of 0.07 ± 0.05 and 0.06 ± 0.02 K day-1, respectively. This study provides insights into sources of BC over a transport channel to the southeastern TP and the influence of the cross-border transportation of biomass burning emissions from Southeast Asia during the pre-monsoon.