the synthesis of carbon nanotubes (cnts) from methane decomposition by ni-la-al (ni/la/al = 10: 1:9) and ni-al (ni/a1 = 1:1 ) catalysts at 1023 k was studied.catalysts were prepared by a co-precipitation method.during the methane decomposition, a part of gases at the exit of the reactor was analyzed by gas chromatography.the experimental results show that doping la into ni-a1 catalyst improves the catalytic lifetime and the yields of cnts in the methane decomposition.some characteristics of cnts were investigated by tem and xrd.the analyses show that cnts deposited on the ni-la-a1 catalyst have obvious thinner walls, less bend structures and better graphitization than the sample grown over ni-al.these results indicate that the introduction of lanthanum into the nickel-aluminum catalyst leads to significant changes in the morphology and microstructures of the cnts.