Carbon nanotubes have different properties such as high strength and high Young's modulus, thermal and electrical conductivity, chemical reactivity and other unique physical, mechanical and chemical properties. With attention to these properties; they could have various applications in industrial, medicine and agriculture. Carbon nanotubes synthesis by variety methods and each of the mechanisms have precise features that can have specified properties of carbon nanotubes. Arc discharge, laser ablation and chemical vapor deposition are most common methods and Mechano-thermal, electrolysis and flame are others ways for synthesis carbon nanotubes. In this paper, synthesis of carbon nanotubes with common methods and other different methods were compared and discussed.