The development of low-cost, high-purity and high-performance porous carbon is of great significance for promoting the commercial application of supercapacitors. In this paper, porous carbon spheres (PCSs) with excellent electrochemical performance were obtained by carbonization and activation of starch gel spheres as precursor which is prepared by microemulsion process. The obtained PCSs exhibit both microporous and mesoporous structure, showing a large specific surface area of 1117.0 m2 g-1 and exhibiting a high specific capacitance of 221.3 F g-1at a current density of 0.5 A g-1 in aqueous electrolyte (and still displays capacity of 146.0 F g-1 in ion liquid electrolyte). The PCSs//PCSs symmetric supercapacitor (SSC) based on aqueous electrolyte exhibits an energy density of 10.9 Wh kg-1 at a power density of 300.0 W kg-1, whereas that based on ion liquid electrolyte achieves a high energy density of 29.0 Wh kg-1 at 650.0 W kg-1. The study provides a new idea to develop low-cost, high-purity and high-performance porous carbon materials for supercapacitors. © 2020 World Scientific Publishing Company.