In this work, cobalt hydroxide nanocrystal sheet was prepared by one-step electrodeposition with cobalt nitrate as a precursor. The electrocatalytic behavior to NO2- ion of cobalt hydroxide was studied and the electrochemical sensor was constructed. The morphology and properties of Co(OH)2/GCE were characterized by scanning electron microscopy (SEM), elemental energy spectrum analysis (EDX) and electrochemical techniques, and the electrochemical behavior and electrocatalytic mechanism of NO2- ion were rapidly detected by the modified electrode. The results show that the same concentration of NO2- ion has a proportional relationship between different scanning rates and current, and the electrochemical process of the Co(OH)2/GCE interface is controlled by adsorption. Co(OH)2/GCE showed a good electro-catalytic performance for NO2- ions, with a linear range of 1~15 mmol/L and a detection limit of 0.29 mmol/L (S/N=3).The sensor exhibited rapid preparation, good catalytic activity and easy operation, which is suitable for rapid field screening of nitrite.