ABSTRACT：Multi-walled carbon nanotubes (MWCNTs) with high purity were synthesized by a floating catalyst technique suitable for large-scale production. Ethanol and ferrocene were used as the carbon and catalyst precursors, respectively. Thiophene was added to assist the growth. The pristine sample was chemically activated by using KOH at high temperature and the specific surface area increased drastically from ∼65 m2/g to ∼830 m2/g while the graphite structure was maintained. Furthermore, the mean pore diameter was decreased from 21.15 nm to 7.68 nm and pore volume increased from 0.3429 cm3/g to 1.5950 cm3/g. MWCNTs with a high surface area and pore volume would have promising applications in many fields.