Herein, the cost-effective photocatalyst of TiO2/g-C3N4 microspheres/reduced graphene oxide (T-CNS-G) was synthesized through a simplified two-pot hydrothermal procedure and its structure and characteristics were researched by various characterizations. The as-prepared T-CNS-G nanohybirds exhibited obviously enhanced photocatalytic activities (about 90% after 4 h) for Cr(VI) removal and good cycle stability (five cycles), which was irradiated by visible light. The increased photocatalytic activity of T-CNS-G photocatalysts is the result of the positive synergy of TiO2 nanoparticle, g-C3N4 microspheres, and rGO nanosheets. The synergy made the composite catalyst have a larger specific surface area, stronger visible light absorption capacity, lower fluorescence intensity, and higher photocurrent intensity, thereby increasing the active site of the catalysts and the mobility of photoinduced carriers. In addition, the possible photocatalytic reaction mechanism for a high-efficiency removal of Cr(VI) was proposed by combining the theoretical calculation with experimental testing, which shows that photoinduced electrons reduced Cr(VI) to Cr(III) through photocatalytic reaction.