A series of graphene/titanate nanotubes (TNTs) photocatalysts using graphene and nanoscale TiO(2) or P25 as original materials were fabricated by hydrothermal method. Both low hydrothermal temperature and proper amount of graphene are propitious to better photoactivity. The photocatalytic activities of these nanocomposites far exceed that of P25, pure TNTs and reported TiO(2)-based nanocomposites for the degradation of Rhodamine-B under visible-light irradiation. These prepared photocatalysts were characterized by TEM, XRD, XPS, BET, FTIR and UV-vis diffuse reflection spectra, and the results indicate that the outstanding photoactivities in visible-light region result from sensitization effect of graphene rather than impurity level in the band gap of TNTs. Furthermore, large BET surface areas of these photocatalysts (almost 10 times larger than that of previously reported graphene/TiO(2) nanoparticles) evidently enhance their absorption abilities and photocatalytic performances (the rate constants of degrading Rhodamine-B are at least 5 times higher than that of previously reported photocatalysts). These photocatalysts show good stability, and their photoactivities do not obviously decrease after four times of repeated uses. A detailed photocatalytic mechanism is suggested, as well.