Abstract: Several most important reactions of the process were analyzed, and the basic laws about the operation parameters on the effect of absorption operation were proposed. Meanwhile, the equilibrium stage model based on reaction rate was developed and used for the actual example of the absorption process of NOx gas. The calculation results verified the correctness of the model. Several parameters such as temperature, pressure and oxygen content were studied on the absorption process in another case, which proved this model could be used for the design and operation of the absorption process of nitric gases in water.