A series of visible-light-induced 2D/2D layered g-C 3 N 4 /Bi 12 O 17 Cl 2 composite photocatalysts were successfully synthesized by a one step chemical precipitation method with g-C 3 N 4 , BiCl 3 and NaOH as the precursors at room temperature and characterized through XRD, FTIR, XPS, TEM, BET and UV-vis DRS measurements. The results of XRD, FTIR and XPS indicated that g-C 3 N 4 has been introduced in the Bi 12 O 17 Cl 2 system. The TEM image demonstrated that there was strong surface-to-surface contact between 2D g-C 3 N 4 layers and Bi 12 O 17 Cl 2 nanosheets, which contributed to a fast transfer of the interfacial electrons, leading to a high separation rate of photoinduced charge carriers in the g-C 3 N 4 /Bi 12 O 17 Cl 2 system. Rhodamine B was considered as the model pollutant to investigate the photocatalytic activity of the resultant samples. The g-C 3 N 4 /Bi 12 O 17 Cl 2 composite showed a clearly improved photocatalytic degradation capacity compared to bare g-C 3 N 4 and Bi 12 O 17 Cl 2 , which was ascribed to the interfacial contact between the 2D g-C 3 N 4 layers and Bi 12 O 17 Cl 2 sheet with a matched energy band structure, promoting the photoinduced charges' efficient separation. Finally, combined with the results of the trapping experiment, ESR measurements and the band energy analysis, a reasonable photocatalytic mechanism over the 2D/2D layered g-C 3 N 4 /Bi 12 O 17 Cl 2 composite was proposed.