Abstract: Vertically aligned carbon nanotubes (CNTs) was prepared on porous Al₂O₃ substrate by the CVD method with ferrocene as catalyst precursor, acetylene as carbon source and NH₃, N₂ as carrier gases. Raman spectrum, scanning electron microscope (SEM), high-resolution electron microscope (HRTEM),X-ray diffraction (XRD) and elemental analysis were employed to characterize the materials.Experiment results showed that CNTs grown in NH₃ were bamboo-shaped structure at 800℃, containing about 3.46%(mass) N element and had a space between graphitic layers about 0.384 nm. Moreover, Fe₃C and Fe₂N or Fe₃N compound were detected in the carbon product.Catalyst surface property changed as a result of the NH₃ adsorption in Fe catalyst and adulteration of N in the CNTs made the CNTs show some crystal distortion and a low graphitic degree. CNTs diameter increased with reaction temperature.