Bio-char (BC) samples were modified by the dielectric barrier discharge (DBD) plasma method to enhance the adsorption capacity for gaseous mercury (Hg-0). The discharge gases and treatment time were studied for their influences on surface modification. Surface characteristics of BCs were investigated using nitrogen adsorption method and X-ray photoelectron spectroscopy (XPS) analysis. Hg-0 adsorption performance of BCs was tested in a bench-scale fixed bed reactor. The results indicated that surface area and pore volume of samples decreased slightly with the plasma treatment. Oxygen-containing functional groups (OCFGs) especially C=0 groups increased on carbon surface as a result of the reaction with reactive intermediates. Adsorption data showed that BCs with DBD plasma treatment had higher mercury removal efficiency compared with that of raw BC Oxygen and water vapor were favorable to surface modification in the process of DBD treatment inthis study. Chemisorption was believed to be predominant in Hg-0 adsorption process and carbonyl and ester groups might play the key roles. Compared with commercial activated carbons, the modified BC showed an excellent adsorption performance, implying that DBD plasma treatment was a potential surface activation technology to improve Hg-0 adsorption capacity on bio-char adsorbents. (C) 2016 Elsevier B.V. All rights reserved.