The La-doped powder-form ZnO samples were prepared by impregnation using appropriate amounts of aqueous solutions of La(NO3)3. The non-impregnated and impregnated zinc oxide materials were then thermally treated at different temperatures – 350oC and 450oC in air atmosphere. The phase composition and structure of the obtained catalysts were characterized by powder X-ray diffraction analysis (PXRD), EPR and X-ray photoelectron spectroscopy. The PXRD results gave evidence that the average crystallite size of nanosized ZnO phase was varying within the range of 10-14 nm. The present work was focused on the influence of La doping and calcination temperatures on the photocatalytic activities of zinc oxide samples in the reaction of oxidative degradation of industrial textile azo dye Reactive Black 5 (RB5) under UV-light irradiation. The photocatalytic activity tests showed that the La doped ZnO photocatalysts are superior to the non-doped samples and are applicable to decontamination of the textile waste waters.