The Ni catalyst was deposited on multi-walled carbon nanotubes using electroless-plating method. The experimental results show that not only the concentrations of the compositions such as NaOH, HCHO (formaldehyde solution) (38 wt.%) and C 4 H 4 O 6 KNa·4H 2 O (Rochelle salt crystal) in Ni bath affect the rate of Ni deposition greatly, but also the acid pretreatment of carbon nanotube precursors have a great influence on Ni content and Ni particle size deposited on the surface of the carbon nanotubes and hence the catalytic properties of Ni/CNT in the synthesis of new carbon nanotubes.