With supercapacitors application promotion, looking for simple, energy efficient and environment-friendly method for expandable production of carbon materials with uniform heteroatoms doping as high-performance electrode materials for supercapacitors becomes the keystone of current research. Here, we present a simple, not costly, low environmental pollution method for preparation of nitrogen and oxygen dual-doped activated carbons via one step direct carbonization of natural, renewable and abundant amaranthus followed by ultrasonic treatment with nitric acid. Most noteworthy is XC-700-50, which exhibits high conductivity, moderate surface area, reasonable pore size distribution and high O and N doping contents (12.05% and 5.31% respectively). Benefiting from these features, it displays high gravimetric capacitance (326 F g(-1) and 294 F g(-1) at 0.5 A g(-1) and 1 A g(-1), respectively), good rate capability, as well as excellent cycling stability (about 97.1% and 94.4% of capacitance retention after 10000 cycles at 2 A g(-1) and 10 A g(-1), respectively) in the high mass loading electrode (8 mg cm(-2)), making it a promising electrode material for supercapacitors.