Utilizing biomass as a precursor for preparing heteroatom-doped multilevel gradient carbon with few usage of chemical reagents and by a facile fabrication process is still a great challenge. Herein, a naturally preprocessed biomass product is elaborately chosen as the precursor, and it is directly converted into a multilevel gradient structural N, S co-doped carbon without complicated chemical pre-treatment process. As a result, using the naturally preprocessed biomass product as the precursor not only greatly reduces the usage of chemical activation agents but also endows the obtained porous carbon plentiful mesopores and a high specific surface area. Specifically, the carbon materials exhibit excellent electrochemical properties for supercapacitor. This work anticipates to provide new perspectives for the direct synthesis of high quality porous carbon materials with naturally pre-treated biomass as precursors.