Hydrogel electrolytes have currently emerged as a research hotspot in the construction of flexible supercapacitors. However, the progress in developing hydrogels as quasi-solid electrolytes still faces challenges, such as low ionic conductivity and restricted flexibility. Herein, we developed a novel amphoteric hydrogel electrolyte (SML/QCS/PVA) with high ionic conductivity and flexibility, and proposed a rapid ion transport mechanism to enhance ionic conductivity. Through lignin sulfomethylation and chitosan quaternization, abundant charge groups were introduced to the structure of hydrogel electrolyte to achieve charge modification. These charge groups not only promoted the dissociation of KOH, but also formed ion transport channels to enhance the migration of K+ and OH-. Finally, we seamlessly integrated this electrolyte into a supercapacitor, resulting in a flexible device with high energy density.For the design and development of hydrogel electrolytes, it is crucial to have properties such as high ionic conductivity, excellent flexibility, good mechanical strength, and biocompatibility. In this work, SML/QCS/PVA demonstrated a highly ionic conductivity of 46.64 mS·cm-1, a tensile strain of 927.32%, and compressive strain to 85% in ambient air. Meanwhile, the hydrogel electrolyte had significant antibacterial activity, enhancing its practical applicability. Subsequently, the assembled flexible supercapacitor (SC-SML/QCS/PVA) showcased outstanding capacitive performance, achieving a notable specific capacitance of 192.55 F·g-1 and a high energy density of 45.2 Wh·kg-1 at a current density of 0.5 A·g-1. SC-SML/QCS/PVA also demonstrated exceptional rate performance and cycle stability, maintaining nearly constant coulomb efficiency (99.65%) and retaining 86.13% of capacitance retention after 10000 charge-discharge cycles. Without any external assistance, SC-SML/QCS/PVA could efficiently and safely function under bend and load conditions, showing good deformation adaptability. This work involves several basic and cutting-edge themes, including the construction of hydrogel electrolytes and the investigation of the rapid ion transport mechanism, as well as the application of hydrogel electrolytes in all-solid-state flexible supercapacitors.