Abstract: The effect of temperature and reaction time on the growth of SWCNTs was investigated in a lab-scale fluidized bed reactor using Fe/MgO as catalyst for the easy purification of the as-grown product. Methane was used as the carbon source and online gas chromatography was used to obtain the real-time conversion of methane. The products were characterized by TEM, TGA and Raman spectroscopy. It is found that a low reaction temperature leads to a low activity of the catalyst, while a high temperature increases the deactivation of the catalyst. The optimum temperature was found to be 900℃. High quality SWCNTs were formed within ten minutes and amorphous carbon was found for a longer reaction time.