Multi-walled carbon nanotubes (CNTs)/manganese dioxide (MnO2) nanocomposites were fabricated using the low-temperature hydrothermal method with no oxidant addition as hybrid supercapacitors. The electrochemical behaviors of CNTs-MnO2 were systematically investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The specific capacitance was promoted from 30.3 F g(-1) to 405.15 F g(-1) with a hydrothermal reaction time of 5 min. Compared to pristine CNTs, the improvement ratio of the specific capacitance of a hydrothermal reaction time of 5 min was 13.4 times under the condition of a 1 M Na2SO4 electrolyte at a scan rate of 100 mVs(-1). The CNTs-MnO2 electrode also demonstrated better cycling stability after 1000 cycles. Moreover, this study demonstrates that CNTs-MnO2 electrodes have a low-temperature facile synthesis, high specific capacitance, and good cycle stability. Thus, these good supercapacitors electrodes are promising for the development in energy-storage devices in the future. (c) 2019 The Electrochemical Society.