Small gold particles having sizes of 1.0–2.0nm were deposited on the surface of the sodium trititanate (Na 2 Ti 3 O 7 ) nanotube by the ion exchange method. This nanotube-supported gold catalyst was able to oxidize CO at the sub-ambient temperature. In a pulse reactor, the gold catalyst could achieve a T 50% of 218K using 1.0 vol.% CO/He gas pulses (0.34μmol CO/pulse). In the Au loadings of 0.39–2.53wt.%, the activity of the gold catalyst increased with the gold loading. Calcination of nanotube support at higher than 383K prior to the gold deposition produced a catalyst with a lower activity. Regarding the effect of calcining the gold particles on the activity (with NaTNT support calcined at 673K), the catalyst with gold particles heated at 383K only exhibited the best CO oxidation activity. XPS indicated that there are three gold species with different oxidation state, Au 0 , Au +1 and Au δ− , in the calcined gold catalysts. As calcination temperature increased, the Au 0 concentration increased at the consumption of Au +1 species, while the Au δ− concentration remained relatively constant. This fact strongly suggested that Au +1 species must play an important role in the activity in the sub-ambient temperature region.