Novel graphitic carbon nitride/KTaO3 (g-C3N4/KTaO3) nanocomposite photocatalysts have been successfully synthesized via a facile and simple ultrasonic dispersion method. Compared to either g-C3N4 or KTaO3, the composite photocatalysts show significantly increased photocatalytic activity for degradation of Rhodamine B (RhB) under visible light irradiation. The increased photocatalytic performance of the composite could be attributed to the enhanced photogenerated charge carrier separation capacity. Moreover, it is observed that ∙O2- is the main active species in the photocatalytic degradation of RhB using the g-C3N4/KTaO3 composite photocatalysts.