Carbon nanotubes (CNTs) have been the focus of research in the past two decades due to their fascinating properties and significant potential for a range of applications, from electronics to high performance polymers. In this research multiwalled CNTs, with a diameter of 50 nm and a wall thickness around 5 nm were successfully prepared via microwave induced pyrolysis of guimwood at 500 degrees C. The mechanism for the growth of such CNTs is under microwave irradiation Volatiles were released from the biomass and left behind char particles. These char particles then acted as the carbon source gas. The volatiles were then undergoing thermal and/or catalytic cracking on the surface of char, forming the amorphous carbon nanospheres the carbon nanospheres then subsequently self-assembled into multiwalled CNTs under the effects of microwave irradiation.