An increasing number of focus has been paid to the study of supercapacitors in the context of the increasing demand for energy storage. As an important component of supercapacitors, the electrolyte has become a focus of research. In this work, an inexpensive and readily approach for synthesizing the polymer electrolytes was established by introducing multi-walled carbon nanotubes (MWCNTs) as the filler on the basis of cross-linked chitosan (CS) and poly-(diallyldimethylammonium chloride) (PDDA), followed by a facile ion-exchange in the KOH solution. The resultant MWCNTs-CP-OH- membrane manifests superb chemical stability, high hydroxide conductivity (0.033 S cm(-1)), and enhanced mechanical/chemical properties. Consequently, the fabricated all-solid-state supercapacitors using MWCNTs-CP-OH- composite membrane as a polymer electrolyte displayed prominent cyclic stability over 4000 cycles with 75.3% retention of the capacitance. Aforementioned merits make the MWCNTs-CP-OH- membrane highly promising candidate electrolyte material in all-solid-state supercapacitors.