In this study, the photocatalytic activity of the PbS-CdS/Ti6O13 nanocomposite prepared by sono-intercalation method was evaluated by the degradation of Reactive Black 5 (RB5) as a water pollutant under sunlight irradiation. Strong photocatalytic activity was observed due to the improved light harvesting property of photocatalyst, significant decrease in bandgap energies and heterogeneous electron transfer from CdS and PbS as a guest to K2Ti6O13 as a host. The RB5 concentrations in the solution and on the surface of PbS-CdS/Ti6O13 nanocomposite were measured during the experiment. The effects of some important parameters such as ultrasonic amplitude and initial composite ratio were studied in the synthesis of nanocomposite. The activity of synthesized nanocomposites on the dye degradation was evaluated and the stability and photocorrosion resistance of the catalyst were studied in this work too. In addition, the mechanism of separation of the photogenerated electrons and holes in the PbS-CdS/ Ti6O13 nanocomposite was investigated. The responsible superior active species for the photodegradation activity were explored and a possible mechanism was suggested. (C) 2016 Elsevier B.V. All rights reserved.