Enriching the active sites of catalysts and artificially regulating the directional migration of photogenerated carriers are effective means to improve the catalytic activity of photocatalysts. In this work, polyvinylpyrrolidone (PVP) is used as the morphological modifier to prepare MoSx with three-dimensional (3D) nanoflower structure. Compared with two-dimensional (2D) MoSx nanosheets, three-dimensional nanoflower structure weakens the van der Waals force between nanosheets and inhibits the stacking between layers, thus exposing the high-density active sites of MoSx nanoflower. The CoWO4 nanoparticles are successfully anchored to MoSx by in-situ growth, forming the MoSx/CoWO4 p-n heterojunction photocatalyst. The high photosensitivity of MoSx increases the utilization of MoSx/CoWO4 p-n heterojunction to visible light. The unique 3D nanoflower structure of MoSx results in that CoWO4 nanoparticles are dispersed well on the surface of MoSx, which prevents CoWO4 agglomeration. Based on the high efficiency of charge separation, abundant active sites and excellent property of visible light response, the hydrogen evolution rate of MoSx/CoWO4-40 reached 9414.4 mu mol g(-1) h(-1). (C) 2020 Elsevier Inc. All rights reserved.