In this study, a novel nitrogen-doped biochar oxygen reduction reaction cathode-water hyacinth carbon, was prepared by ZnCl2 molten salt carbonization without additional nitrogen source, which displayed a high performance in electro-Fenton (E-Fenton) process. The BET result shows that water hyacinth carbon achieved a much larger specific surface area (829 m(2).g(-1)) than non-melt salt carbonized one (323 m(2).g(-1)) and graphite powder (28 m(2).g(-1)). Furthermore, characterization by XPS and EIS shows that both pyridinic-N (43.24%) and graphitic-N (56.75%) existed in water hyacinth carbon and Warburg constant was only 0.051. Because of a high H2O2 producing yield 1.7 mmol.L-1 and corresponding current efficiency 81.2 +/- 2.5% in molten salt carbonized water hyacinth biochar, a high kinetic constant 0.318 min(-1) in DMP degradation was achieved, which was 4 times higher than graphite powder (0.076 min(-1)). The TOC removal achieved 86.8% in 30 min and the corresponding energy consumption reached a low level 60.15 kW.h.kgTOC(-1).