It is essential to improve the activity of Bi2WO6 for the photocatalytic 2,4-dichlorophenol (2,4-DCP) degradation by modulating the visible-light excited photogenerated electrons. As for this, Bi2WO6 nanostructures have been synthesized by a mannitol assistant hydrothermal method. It is shown that the temperature-optimized Bi2WO6 exhibits high photocatalytic activity for 2,4-DCP degradation under visible-light irradiation, attributed to the coral-like structure, high crystallinity and large surface area. Interestingly, the photocatalytic activities of coral-like Bi2WO6 could be further improved by coupling ultrafine nanocrystalline SnO2. It is confirmed mainly from the steady-state and transient-state surface photovoltage responses and fluorescence spectra related to the formed hydroxyl radical amounts that the coupled SnO2 is taken as a proper energy platform to accept the visible-light excited high-energy-level photogenerated electrons from Bi2WO6, consequently enhancing the charge separation and prolonging the charge lifetime. Moreover, the optimized SnO2-coupled BWO exhibits higher photocatalytic activity under UV-vis light irradiation than the commercial P25 TiO2. This work will provide a new feasible route to prepare highly efficient Bi2WO6-based photocatalysts for purifying chlorophenol-polluted water environments.