A series of Bi2S3/(BiO)(2)CO3 composite photocatalysts with different loadings of amorphous Bi2S3 were successfully synthesized through an ultrasonic-assisted ion-exchange reaction between thioacetamide (CH3CSNH2) and (BiO)(2)CO3, and characterized by XRD, XPS, BET, EELS, EDX, SEM, TEM/HRTEM, UV-Vis, and photoluminescence (PL) techniques. The results of TEM/HRTEM, EELS, and EDX indicate that the composite catalyst Bi2S3/(BiO)(2)CO3 has been successfully synthesized with the deposited Bi2S3 present in amorphous state on the surface of (BiO)(2)CO3. The activities of the catalysts for RhB degradation under visible light show that the catalyst prepared under ultrasonic is more active than the one synthesized without ultrasonic. The optimized sample Bi2S3/(BiO)(2)CO3 (U5.0) exhibits a much higher activity, about 4.8 times to that of pure (BiO)(2)CO3. Based upon the band structures of Bi2S3/(BiO)(2)CO3, it is deduced that the migration of the visible light-induced electrons from the conduction band of Bi2S3 to that of (BiO)(2)CO3 should have facilitated the separation of photogenerated carriers, as confirmed by the suppressed photoluminescence spectra. Using different scavengers, the center dot O-2 (-) and holes are clearly identified as the main oxidative species for RhB photodegradation. In light of these observations, a potential photocatalytic mechanism of RhB degradation over Bi2S3/(BiO)(2)CO3 is proposed.