A series of Ag-ZnO/CNT nanophotocatalysts with different multiwall carbon nanotubes loadings were prepared by precipitation-decomposition method. The samples properties were well-characterized by XRD, FESEM, EDX, BET, FTIR and DRS measurements. The results indicated that the loading of multiwall carbon nanotubes to nanocomposites has significant influences on morphology, surface area, hydroxyl and carboxylic functional groups and the absorption of visible light region. The catalytic performance was evaluated by the photo catalytic degradation of Acid Orange 7 dye under visible light. The results revealed that the Ag-ZnO/CNT(5) nanophotocatalyst with 5 wt.% loading of functionalized multiwall carbon nanotubes possessed superior photocatalytic activity than that of Ag-ZnO nanocomposite and the pure ZnO. The enhanced photocatalytic activity was attributed to the effective separation of electron-hole pairs on Ag-ZnO/CNT. The effect of operational parameters such as the initial pH, amount of photocatalyst and dye concentration on photo mineralization of AO7 dye has been analyzed, which efficient degradation was observed at pH 3-9. Furthermore, Ag-ZnO/CNT(5) nanophotocatalyst exhibited good recycling stabilities over several separation cycles in photocatalytic reaction system. Finally, a mechanism for photocatalytic degradation of AO7 dye is suggested. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.