N/S doped carbon nanotubes were prepared with natural mineral fibrous brucite as template, sucrose as carbon source, and thiourea as nitrogen and sulfur source. Experimental results indicate that the doped carbon nanotubes inherit the one-dimensional columnar structure of the fibrous brucite template. In addition, it presents a hollow tubular structure, which increases the specific surface area and pore volume of the template carbon. In 6 mol·L^-1 KOH electrolyte, the electrochemical performance significantly improves after doping. CNT-N/S presents a high specific capacity of 172.0 F·g^-1 at current density of 1 A·g^-1, higher than those of CNT (62.2 F·g^-1) and CNT-N (97.0 F·g^-1). The capacitance of the N/S doped carbon nanotubes remains 89% after 1000 charge-discharge cycles. Furthermore, the assembled symmetrical supercapacitor also shows good capacitance performance.