A post-oxidation strategy was proposed to synthesize sulfonated graphene nanosheets/carboxylated multi-walled carbon nanotube-supported PANI (sGNS/cMWCNT@PANI) hierarchical nanocomposites by an interfacial polymerization as advanced supercapacitor electrodes. Field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HRTEM) indicated that the morphology with a coexisting structure of sGNS supported PANI nanorod arrays and coaxial cMWCNT/PANI nanocables did not show significant differences through a post-oxidation process. X-ray diffraction (XRD) and thermogravimetic analysis (TGA) proved that the oligomers of PANI were eliminated during the post-oxidation process. The spectral analysis revealed that the post-oxidation led to an increasing content of quinoid structure in the nanocomposites. Electrochemical measurements showed that the sGNS/cMWCNT@PANI with a post-oxidation process exhibited improved cycling stability with 91.4% capacitance retention after 5000 cycles.