Biomass-derived porous carbon materials stimulate considerable research interest owing to the abundant resources, low cost, eco-friendliness and effective applications in electrochemical energy storage. Herein, N/S/O-doped honeycomb-like porous carbon materials are successfully controlled prepared from green bristlegrass seeds by one-step carbonization with assistance of gelatinization treatment. Benefitting from their three-dimensional interconnected honeycomb-like hierarchical porous architecture together with high specific surface area and multi-heteroatom doping, the as-synthesized carbon materials exhibit high specific capacitance of 391 F g(-1) at a current density of 0.5 A g(-1) with good rate capability (67.8% capacitance retention at 50 A g(-1)) in 6 M KOH and outstanding cycling stability with a capacitance retention of 97.2% over 10000 cycles. Meanwhile, the symmetric supercapacitor device in 1 M Na2SO4 aqueous electrolyte is able to deliver a high energy density of 20.15 Wh kg(-1) at a power density of 500 W kg(-1) with a wide voltage window of 2.0 V. More impressively, it still retains a high energy density of 15.56 Wh kg(-1) even at 20 kW kg(-1). In addition, the supercapacitor device also shows superior cycling performance with a 94.2% capacitance retention for 10000 cycles.