Bamboo-like carbon nanotubes containing sulfur (BCNT-S) were prepared through the carbonization and the activation of sulfonated polymer nanotubes in CO2. The BCNT-S showed a remarkably high specific capacitance of 259Fg−1 at the current density of 1Ag−1, while 97.7% of its initial capacitance was retained after 1000 cycles at the current density of 5Ag−1. In contrast, amorphous carbon without S had a specific capacitance of 129Fg−1 at 1Ag−1, which was only about half of that of the BCNT-S. Therefore, the introduction of a trace amount of sulfur (1.66%) could greatly enhance the specific capacitance of carbon nanotubes (CNTs). In addition, the high specific capacitance and excellent cycling stability of the BCNT-S were also benefited from its high specific surface area and bamboo-like tubular morphology.