Here, we report a composite photocatalyst Bi2O2CO3/Bi2WO6 which was successfully prepared via a two-step hydrothermal method assisted by Ag nanoparticles. The use of Ag nanoparticles is promoting the production of Bi2O2CO3 by oxidizing ethylene glycol and to obtain the most suitable heterogenous structure. The synthesized Bi2O2CO3/Bi2WO6 photocatalyst possesses larger specific surface areas than pure Bi2O3 and pure Bi2WO6 samples. The complex structure of Bi2O2CO3/Bi2WO6 benefits the separation of photogenerated electrons and holes since its photoluminescence intensity of emission peaks were dramatically weakened. With larger specific surface areas and lower photogenerated electron-hole pairs recombination rate, Bi2O2CO3/Bi2WO6-3% composite exhibits the highest photocatalytic activity among all samples when photodegrading gaseous pollution under visible light (lambda > 420 nm). The photocatalytic activity of Bi2O2CO3/Bi2WO6-3% composite was 2.05, 3.41 and 10.19 times than that of Bi2O2CO3/Bi2WO6, pure Bi2O3 and pure Bi2WO6, respectively. Finally, a possible charge separation mechanism was proposed to explain the improved photocatalytic activity of Bi2O2CO3/Bi2WO6 composite.