CoS is one of the ideal electrode materials for supercapacitor, but its long-term stability and electrochemical performance needed to be improved before its successful application. Uniformly embedding carbon nanotubes (CNTs) inside the CoS matrix can provide numerous and effective diffusion paths of electrons and electrolyte ions, which can reduce the charge-transfer resistance and effectively improve the electrochemical performance of CoS. In this work, nanocomposites of Co2(CO3)(OH)2 and CNTs were prepared using a facile hydrothermal method, and then were transformed into CoS1.29@CNTs nanocomposites via an ion-exchange process. The carbon nanotubes were uniformly embedded inside the CoS1.29 matrix. When the amount of CNTs was 6.1 wt%, the CoS1.29@CNTs electrode exhibited a higher specific capacitance (99.7 mAh g-1) than that of CoS1.29 electrode (84.1 mAh g-1) at a current density of 1 A g-1 measured in 2 M KOH electrolyte. The asymmetric supercapacitor assembled with the CoS1.29@CNTs-6.1% electrode and an activated carbon (AC) electrode exhibited an energy density of 39.1 Wh kg-1 at a power density of 399.9 W kg-1. Moreover, the specific capacitance of the CoS1.29@CNTs-6.1%//AC device maintained 91.3 % of its original value after 2000 cycles at a current density of 3 A g-1.