Recently, the preparation of porous carbon using biomass materials as carbon precursor has received extensive interests due to their wide range of sources and low cost. Herein, ultrasonic-assisted fabrication of porous carbon materials derived from agricultural waste had been successfully synthesized and further applied in solid-state supercapacitor. It is found that the adoption of ultrasonic-assisted method could deeply etch carbon materials to induce more porous structure to the resulted carbon materials. The presence of additional pore structures is beneficial for the transfer of electrolytes, providing more active sites and improving electrochemical performance. Compared with the samples without ultrasonic treatment, the activated sample exhibits a high specific surface area of 1281 m 2 /g, abundant porous structure and prominent specific capacitance of 197 F/g. The assembled symmetrical solid-state supercapacitor shows a high energy density of 18.43 μWh/cm 2 at 120 μW/cm 2 and predominant cycle stability with 86% capacitance retention even after 2500 cycles at high current density of 3 mA/cm 2 . The obtained results predicted that ultrasonic-assisted fabrication of porous carbon materials exhibits great application potential for flexible supercapacitors.