CuO nanoflowers made up of nanobelts (CuO NFNBs) were successfully prepared in one step by a simple and reliable seed-mediated route, employing only Cu(NO3)(2) and NH3-H2O as the starting materials. The as-prepared sample was characterized by XRD, FESEM, and TEM techniques: The growth mechanism of these nanostructures is discussed. A glassy carbon electrode modified with CuO NFNBs was then used to detect hydrazine. The results show that the CuO NFNBs show a very high activity for detecting hydrazine.