Herein, we use a facile one-pot strategy to synthesis hierarchical porous carbon from sodium alginate (SA). After pre-conditioned at 200 °C, SA was activated by a small amount of NaOH at 800 °C. In the sintering process, the SA can achieve a self-activation effect which can effectively reduce the dosage of alkaline activator (in a weight ratio of 5:4) during activating process. Finally, the end product exhibits a capacity of 451 F/g in 2 M KOH aqueous solution and exhibit excellent rate ability. The cycle ability of OSADC-5 was tested at 10 A/g, and after 10,000 cycles the capacitance retention is 99% which shows superb electrochemistry stability.