In this study, the electrochemical capacitor characteristics of vertically aligned carbon nanotubes (VACNTs) with different nitrogen content were investigated. The pristine VACNTs and nitrogen-doped VACNTs were synthesized by thermal chemical vapor deposition (CVD) with a mixture of C 2 H 2 and NH 3 gases. The content of nitrogen doped into VACNTs played an important role in enhancing the capacitance characteristics. With increasing the NH 3 pressure, the nitrogen content of VACNTs increased. However, the capacitance did not increase with the increase in nitrogen content of VACNTs entirely. There was an optimal NH 3 pressure for synthesizing the nitrogen-doped VACNTs to obtain the maximum capacitance. Furthermore, for the real practice of supercapacitor, the stability of capacitance was tested for 500 cycles. The results revealed that the nitrogen-doped VACNT was a promising supercapacitance device material.