Abstract: A simple,rapid and accurate kinetic method for the determination of purity of carbohydrazide product was described.The method was based on the reaction between carbohydrazide and malachite green to form a colorless compound.The apparent reaction rate constant was determined and the reaction mechanism was studied.The linear calibration curve was in range of 4×10-3~50×10-3mol·L-1 for carbohydrazide with a limit of detection of 1.0×10-3mol·L-1.The method has been applied to the determination of purity of carbohydrazide product.