As metal-free visible light-driven semiconductor, graphitic carbon nitride (g-C3N4) has attracted increasing attention owing to its excellent properties. However, the photocatalytic performance of the bare g-C3N4 has been significantly hampered by its inherent drawbacks. Herein, to further boost the photocatalytic performance of g-C3N4 , Bi2WO6 was in-situ successfully anchored onto g-C3N4 via a routine hydrothermal method. The as-prepared Bi2WO6/g-C3N4 heterojuctions display highly efficient photocatalytic activity toward decay of rhodamine B (RhB) and phenol aqueous solution under simulated sunlight irradiation. When the molar ratio of Bi:g-C3N4 was 4%, the Bi2WO6/g-C(3)N(4 )sample prepared exhibits highest photocatalytic activity. The highest photocatalytic performance of the 4% sample can be definitely attributed to the highest separation rate of the photogenerated electron-hole pairs, supported by the results of surface photovoltage spectroscopy (SPS). The cycling experiments show that Bi2WO6/g-C3N4 composites display excellent stability. The photoinduced electron-hole separation and transfer of the Bi2WO6/g-C3N4 composites obey a direct Z-scheme mechanism based on the matched energy band, the analysis of main active species and the enhanced separation rate of photogenerated electron-hole pairs.