Nitrogen and sulfur co-doped porous carbon (NSCDPC) was prepared by a one-step method using purple-leaf plum kernel shell, potassium benzoate, and N,N’-diphenylthiourea (DPTU) as carbon precursor, activator and nitrogen and sulfur source, respectively. The use of potassium benzoate with weak alkalinity and causticity facilitates obtaining abundant microporous structure and heteroatoms. Meanwhile, the dopant N,N’-diphenylthiourea plays a synergic activation role. The optimal layer-stacked NSCDPC750-1 exhibits abundant ultramicropores and defect sites, developed interconnected channels, large specific surface area, and rich nitrogen and sulfur contents, resulting in excellent electrochemical performance. As expected, NSCDPC750-1 displays a high specific capacitance of 338 F g-1 at 0.5 A g-1 in 6 M KOH electrolyte, outstanding rate performance with 280 F g-1 at 20 A g-1, and remarkable durability with 92.3% retention after 10000 cycles. In addition, the symmetric supercapacitor assembled with NSCDPC750-1 as electrode and 6 M KOH as electrolyte possesses an outstanding specific capacitance of 111 F g-1 at 0.5 A g-1, excellent rate capability, and high energy density of 30.22 Wh kg-1. The impressive electrochemical performance makes NSCDPC750-1 a promising supercapacitor electrode material.