Single-walled carbon nanotubes (SWNTs) were prepared by continuous wave CO2 laser ablation without applying additional heat to the target. Transmission electron microscope and Raman spectrum were used to investigate the effect of laser power on the growth and diameter distribution of the tubes. The average diameter of single wall carbon nanotubes produced by CO2 laser increases with increasing laser power. We have presented the radial breathing mode of Raman spectrum of SWNTs prepared by using CO2 continuous laser vaporization in laser power from 500 to 850 W, and the Raman spectrum are also compared with those of single-walled carbon nanotubes produced by pulsed CO2 laser ablation of previous reports. SWNTs and bamboo-shaped carbon nanotubes were observed from web-like carbon soot in a lower laser power of 500 W. Experiment confirmed that laser power play a crucial role in SWNTs formation and diameter distribution.