This work presents the development of a dynamic mathematic model useful for predicting the concentration of hydrogen peroxide used for the decyanidation in wastewater treatment. The quantitative model based on the physical-chemistry classical theory of the decyanidation process developed and validated on Mattlab® with real data of the process of decyanidation. The tool will be useful in decision making for the engineers and operators process involved in the control and supervision during real-time operation of the decyanidation of wawtewater in the metal finishing industry, improving in the process the operating conditions, efficiency, reliability and safety.