The Bi-based bimetallic oxides photocatalyst Bi_7.53CO_0.47O_11.92 was successfully synthesized and the graphite phase carbon nitride (g-C₃N₄) was loaded, and a novel composite photocatalyst Bi_7.53CO_0.47O_11.92/g-C₃N₄ was obtained as well. The photocatalyst Bi_7.53CO_0.47O_11.92, possessed tetragonal crystal structure, with the introduction of g-C3N4, the H₂ production reached the maximum about 108 mu mol under continuous visible light irradiation for 4 h, which was 13 times higher than that of pure g-C₃N₄ photocatalyst. A series of studies shown that the g-C₃N₄ on the surface of Bi_7.53CO_0.47O_11.92 provided the more active sites and improved the efficiency of photo-generated charge separation by means of several characterizations such as SEM, XRD, XPS, element mapping, UV-vis DRS and FTIR. etc. and the results of which were in good agreement with each other. The composite photocatalyst Bi_7.53CO_0.47O_11.92 has a greater specific surface area and pore volume compared to pure g-C₃N₄, which is more favorable for the adsorption of dye molecules, leading to enhance the composite photocatalytic activity consequently. The excited-electron recombination process was greatly modulated with the introduce g-C₃N₄ on the surface of Bi-based bimetallic oxides photocatalyst and the photostability was enhanced as well. The promoted charge separation was measured by means of the EIS, photocurrent and transient fluorescence. In addition, a possible reaction mechanism over eosin Y-sensitized Bi_7.53CO_0.47O_11.92/g-C₃N₄ photocatalyst under visible light irradiation was proposed.