In this paper, hexagonal ZnIn2S4 nanoflowers were grown in situ on tetragonal WO3·H2O nanosheets, yielding a compact ZnIn2S4@WO3·H2O (ZIS@WO) core-shell heterojunction. The formation of the ZIS@WO heterojunction was optimized by meticulously adjusting the quantity of WO3·H2O nanosheets incorporated. The crystal structure and microstructure of ZIS@WO were comprehensively examined using XRD, TEM and EDS analyses. The photocatalytic properties of ZIS@WO heterojunctions were evaluated through the degradation of organic pollutants under visible light irradiation. The results demonstrated a marked enhancement in photocatalytic efficiency for the ZIS@WO heterojunction. Further investigation into the separation and transport of photogenerated carriers were performed using PL spectroscopy and photoelectrochemical measurement. Compared to the individual components of ZnIn2S4 nanoflowers and WO3·H2O nanosheets, the ZIS@WO heterojunction creates an internal electric field at the interface, along with a compact core-shell configuration. This internal electric field, in conjunction with the band structure of the heterojunction, effectively accelerates the separation of photogenerated electrons and holes. Additionally, a comprehensive analysis of the photocatalytic degradation mechanisms were presented, elucidating the intricate processes.