As an organic macromolecule rich in oxygen-containing functional groups, lignite is considered as a natural precursor for the preparation of oxygen-enriched porous carbon. Lignite modified by acid washing followed with oxidization (OAWSL) was obtained for increasing the oxygen content. With the activation of KHCO3, a large number of bubbles penetrate the carbon layer and escape to form abundant pores at high temperature, and a unique spherical surface is obtained. What′s more, the effect of the addition of KHCO3 on the structure and the electrochemical performance of porous carbon as electrode material for supercapacitors was investigated. It is found that the porous carbon spheres, which is prepared under the condition of the mass ratio of 1∶3 (OAWSL ∶ KHCO3), have the most uniform spherical structure, the largest micropore occupancy (90.88%) and the highest oxygen content (22.17%). In the electrolyte of 6 mol/L KOH, a specific capacitance of 323 F/g (at the current density of 0.1 A/g) is obtained in the three-electrode system using the porous carbon sphares as electrode material. In addition, the assembled supercapacitor has the maximum energy density of 6.17 Wh/kg. After 20 000 GCD cycles at 2 A/g, the capacitance still retained 96% of initial, and the Coulombic efficiency is always 100%. This paper can provide theoretical support for the preparation of lignite based oxygen-enriched porous carbon materials.