Achieving a simple and mild preparation method to obtain high performance carbon-based flax fiber electrode for supercapacitor has become particularly important but still challenges. Hence, the excellent electrochemical performance of electrode was constructed by impregnation-heat treatment with ethylenediamine tetraacetic acid disodium zinc (EDTANaZn) and zinc nitrate (ZnNO) as activators. The results show that the decomposed zinc oxide (ZnO) of EDTANaZn leads to the prominently hierarchical porous structure and abundant nitrogen-doping, which provides more active storage sites for electrolyte. Likewise, the as-prepared electrode by EDTANaZn treatment exhibits the specific capacitance of 292 F g at the current density of 0.5 A g, and keeps up with the capacitance retention of 102 % even after a 10, 000 long-cycles at the high current density of 10 A g. Significantly, the suitable zinc salt assisted preparation of high performance flax fiber carbon-based electrode provides a novel idea for future electrochemical energy storage.