It has been clearly demonstrated that the visible-light photocatalytic activities of g-C3N4 (CN) for degrading 2,4-dichlorophenol (2,4-DCP) and bisphenol A (BPA) could be improved by fabricating nanocomposites with a proper amount of nanocrystalline anatase TiO2. Interestingly, the visible-light activities of the amount-optimized nanocomposite could be further improved after decorating Au nanoparticles, with 5.11- and 3.1-time improvement respectively for 2,4-DCP and BPA compared to that of CN, even much higher than that of P25 TiO2 under UV-vis irradiation. Based on the transient-state surface photovoltage responses and photoelectrochemical measurements, it is confirmed that the exceptional visible-light activities of the fabricated Au-(TiO(2)g-C3N4) nanocomposites are attributed to the extended visible-light response due to the surface plasmonic resonance (SPR) of decorated Au and its catalytic function, and to the enhanced charge separation by transferring electrons from CN and SPR Au to TiO2 in the nanocomposites. The highly promoted charge separation results in the effective availability of a large number of hydroxyl radicals ((OH)-O-center dot) participating in the photocatalytic oxidation process of 2,4-DCP. Furthermore, a possible mechanism of 2,4-DCP degradation is proposed according to the detailed analyses of produced intermediates. This work provides new idea for designing Au assisted nanocomposite photocatalysts for environmental remediation. (C) 2017 Elsevier B.V. All rights reserved.