The surface-enhanced Raman scattering (SERS) of molecules on TiO2 (Degussa P25) was investigated. The variation of trap density was carried out by the calcination of TiO2 at 350, 450 and 600°C. We found that the SERS intensity increases first, and then decreases with the calcination temperature rising from 350 to 450°C and 450 to 600°C, respectively. The measurements indicate that the trap density increases with the calcination temperature rising. The results indicate that the increase of trap density is favorable for the increase of SERS enhancement. The increase of SERS intensity from 350 to 450°C could be due to the dominated contribution from the trap density increase, and the decrease from 450 to 600°C could be due to dominated contribution from the increase of the crystallite size and the mass fraction of rutile phase. Copyright © 2012 John Wiley & Sons, Ltd.