We report the new roles of graphene oxide (GO) as structure-directing and morphology-controlling agents in the nucleation and growth of heterostructured Bi2MoO6/Bi3.64Mo0.36O6.55 composites. The heterostructured composites have been fabricated through a facile one-step hydrothermal method, among which the interfacial contact between Bi2MoO6/Bi3.64Mo0.36O6.55 and graphene is achieved. The as-prepared composites were characterized by powder X-ray diffraction, UV vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The composition, morphology and structure of the composites can be controlled by regulating the amount of GO used in the synthesis. We proposed a plausible mechanism for their formation, and evaluated them for the photocatalytic degradation of Rhodamine B (RhB). Among them, the 1% graphene-Bi2MoO6/Bi3.64Mo0.36O6.55 (1%G-BMO) composite performs the best. The efficacy of 1%G-BMO is attributed to the optimal Bi2MoO6/Bi3.64Mo0.36O6.55 phase ratio, the unique morphology and structure, as well as the effective separation of photogenerated electrons and holes. (C) 2014 Elsevier B.V. All rights reserved.