Degradation efficiency, product distribution and reaction pathway of N-nitrosodimethylamine (NDMA) photocatalytic degradation over TiO2 nanotube(TiNT), Au-modified TiO2 nanotube(Au/TiNT) and TiO2 nanopowder(TiO2) were investigated to evaluate the tube effect. The results show that TiO2 nanotube was prepared and tubular morphology was kept after Au modification. The degradation efficiencies of NDMA over TiNT and Au/TiNT are significantly higher than that over TiO2 powder, DMA becomes to be the major product, and NO2- production is also detectable, which all stem from the tubular morphology of TiNT and Au/TiNT. In the presence of TiNT and Au/TiNT, the small NDMA molecules enter into the nanotube and lead to a higher concentration and a closer contact in a nanotube structure space, resulting in remarkable high degradation efficiencies of NDMA, and also initiating new photocatalytic reaction pathway derived from effectively contacts between radical intermediate and NO2- products in the nanotube structure. The nanotubular morphology of TiNT and Au/TiNT plays an important role in enhancing NDMA photocatalytic performances. (C) 2016 Elsevier Ltd. All rights reserved.