In this study, activated biochar prepared using Taihu blue algae was adopted to facilitate cathodic hydrogenotrophic denitrification in bioelectrochemical system (BES). It was found that addition of algal biochar (ABC)-800N (treated with nitric acid) at biocathode reached the highest nitrate removal constant (21.79), while the control reached only 6.94. Besides, activity of nitrous oxide reductase attained 5.16 U/L for the control in day 7, while group ABC-800N reached 16.06 U/L by then. Importantly, chronoamperometry (CA) detect indicated an electron exchange capacity for group ABC-800N as 872.68 mu mol e(-)/gBC, compared to 162.81 mu mol e(-)/gBC for the control. Through chronocoulomb (CC), better charge/discharge stability can be concluded in BES reactor using ABC-800N. Therefore, activated biochar could be implemented to enhance denitrification process at biocathode in BES.