Hard carbon is regarded as promising anode materials for potassium-ion batteries (KIBs) owing to their low price and easy availability. However, the limited rate capability still needs to be improved. Herein, we demonstrate the fabrication of oxygen/sulfur co-doped hard carbon through a facile hydrolyzation-sulfuration process of skimmed cotton. The simultaneous dopants significantly improve potassium ion diffusion rate. When served as the anode for KIBs, this hydrolyzed hard carbon delivered a high reversible capacity (409 mAh/g at 0.1 A/g), superior rate capability (135 mAh/g at 2 A/g) and excellent cyclability (about 120 mAh/g overt 500 cycles at 2 A/g). This work provides a facile strategy to prepare low-cost doped-hard carbon with superior potassium storage property.