In order to investigate the removal mechanism of ammonia by biochar three-dimensional electrode, a lab-scale innovative three-dimensional electrode reactor using biochar as reactive media was established, and the removal trend and mechanism of ammonia (in non-chlorine water) during the reactor operation were investigated. Experimental results indicated that the biochar three-dimensional electrode reactor could achieve a high ammonia reduction in a short time (ρ₀=100 mg/L, t=3 h, η=45.72%). The ammonia transform process is a hydroxyl consumption reaction, which fitted well with the first-order kinetic model well, and biochar adsorption contributed insignificantly on bulk ammonia removal, while the direct and indirect oxidation within the reactor would convert the ammonia nitrogen to gaseous nitrogen and nitrate nitrogen instead.