A novel nanoscale powder 20 wt%SrO-CuBi2O4 has been successfully synthesized for the first time by ion exchange through doping Sr(NO3)(2) into CuBi2O4 matrix and characterized using TG/DTA, XRD, EDX, SEM and electrical measurements. The as-prepared 20 wt%SrO-CuBi2O4 composite exhibit much higher photocatalytic activity than 20 wt% SrO-CuBi2O4 synthesized via physical process and pure phase CuBi2O4 under UV-A light irradiation (lambda = 365 nm) in the course of the photocatalytic redox activity of Congo red (CR). Maximum degradation was achieved within 220 min of irradiation time under UV-A light as a result of 97.22% of photocatalytic efficiency of CR. The mechanisms of the enhancement of photocatalytic activity of the nanocomposite photocatalyst will be discussed by the p-n heterojunction principle (charge separation and photochemical diode models) and the valance band theory. The pure nanocomposite systems have been also reported for a comparative purpose. (C) 2012 Elsevier B. V. All rights reserved.