A urea sensor base on reticulated nickel hydroxide is prepared by hydrothermal way and operated by differential pulse voltammetry method. The reticulated nickel hydroxide has been successfully synthesized by a hydrothermal method and has been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The Ni(OH)₂ sensor exhibits a higher sensor response (S) of 7.1 than NiO and Au sensing materials to 0.05 M urea concentration at 0.62 V. Various concentration of urea from 0.1 mM to 50 mM are performed on Ni(OH)₂, and the sensor response are increased from 1.1 to 7.1 by differential pulse voltammetry (DPV) method. The urea detection limit is measured as 0.1 μM in this system. In addition, the Ni(OH)₂ sensor exhibited good reproducibility and short term stability, and the response exhibits no obvious changes after 20 days tests. A possible sensing mechanism of Ni(OH)₂ urea sensor is presented.