The novel hierarchical PANI/sMWCNT nanocomposites were synthesized through the interfacial polymerization method in the presence of the sulfonated multiwalled carbon nanotubes (sMWCNT), and the effect of oxidant content on the chain structure of PANT, the microstructure, and supercapacitive performance of the composites were investigated systematically. FT-IR spectra revealed the presence of pi-pi interactions between PANT and sMWCNT, and the charge-transfer composites were formed. It was found that more charge-transfer composites developed when the oxidant was at a lower content. The FESEM images indicated that the morphology of the composites changed significantly with varying oxidant content. It could be seen from electrochemical tests that the supercapacitive performance of the nanocomposites was influenced markedly by their microstructure, the content, and the oxidation degree of PANI. When the oxidant content was high at 2 for the APS/aniline Mole ratio, the composite had high specific capacitance with 431.3 F/g but showed poor rate performance and charge/discharge stability. At a lower oxidant content with 1/6 of the APS/aniline mole ratio, the specific capacitance of the composite decreased to 216.6 F/g; nevertheless, it possessed superior rate performance with 82.8% capacitance retention at 10 A/g and excellent cyclability with just 11.2% capacitance loss after 2000 cycles.