Humic acid is creatively selected as an anode material in sodium ion batteries. Bio-based carbon fibers (H-CF) are fabricated from polyacrylonitrile (PAN) − humic acid (HA) via simple eletrospinning followed by stabilization and carbonization. The heat-treatment temperature (HTT) is optimized based on analysis of material structures and electrochemical performances. Due to unique composite networks and oxygenic functionalities, the H-CF anode obtained at 1300°C has a large reversible capacity of 261.3mAhg−1 (current density: 0.02Ag−1, initial efficiency: 69.6%). The anode also presents good cycle stability (249.6mAhg−1 reversible capacity at 0.1Ag−1 with capacity retention of 92.8% over 100 cycles) and good rate capability (208.6mAhg−1 at 0.2Ag−1 and 81.7mAhg−1 at 1Ag−1). It is proved that humic acid can serve as a robust precursor for high-performance anode of sodium ion batteries.