This study successfully synthesized Bi2S3/ZnIn2S4 composites with different weight percentages of Bi2S3 by cyclic microwave irradiation followed by wet impregnation. The photocatalytic activities of the Bi2S3/ZnIn2S4 composites were evaluated by the photodegradation of methylene blue in an aqueous solution. It was found that the 12.5%wt-Bi2S3/ZnIn2S4 photocatalyst exhibited the highest decolorization efficiency (95.4% within 300 min) with good stability against photocorrosion and good recyclability for photocatalytic reaction. Based on the results from UV-vis DRS, PL, photocurrent response measurement, and the active species trapping experiments, the enhanced photocatalytic activity of the Bi2S3/ZnIn2S4 photocatalyst was due to the increased ability to absorb visible light, and the enhanced charge separation and transportation between Bi2S3 and ZnIn2S4 through the Z-scheme mechanism. A direct Z-scheme charge transfer pathway for photocatalytic reaction over the Bi2S3/ZnIn2S4 photocatalyst was also proposed and discussed.