The interaction between CNT and its catalyst is provided by van der Waals force. Due to this interaction, the CNT vibrates with a definite frequency. When the van der Waals force minimizes, a carbon may place between the catalyst and tube. By continuing this mechanism the CNT grows. The growth procedure reduces the frequency of nanotube vibrations that decreases the growth rate. This Letter proposes a theoretical model which describes the growth mechanism of the CNT. (c) 2005 Elsevier B.V. All rights reserved.