Zinc oxide nanobelts (ZnO nanobelts) are prepared by chemical precipitation method and used as catalysts in the Knoevenagel condensation of a variety of aldehydes and active methylene compounds using distilled water as a green reaction media. Furthermore, Knoevenagel condensation products were characterized by their spectral analysis. The obtained results will contribute to our understanding of nanotechnology in catalysis and enable a green and efficient protocol for developing olefines.