The photocatalytic activity of pure ZnO and nitrogen doped ZnO was compared by investigating the photodegradation of azure B dye under visible light. The nanophotocatalysts pure ZnO and N-doped ZnO was prepared by precipitation method. The morphologies and structural properties of as-synthesized nanomaterials were investigated by using FT-IR, DRS, XRD and SEM techniques. The results revealed that the N-doped zinc oxide photocatalyst showed higher photocatalytic activity compared to pure zinc oxide. Different rate affecting parameters were also studied.