A mathematic model has been presented to predict the decarburization kinetics of grain-oriented silicon steel sheet in the gas mixture of N2–H2–H2O during annealing.This model is based on the carbon flux balance between the oxidation reaction at the surface and the carbon diffusion inside the steel sheet.It can be numerically solved to quantify the influences of annealing temperature and atmosphere on decarburization kinetics when the boundary conditions are properly determined.In case that a humid gas mixture is employed during annealing,the most influential process parameter is temperature rather than compositions of the gas mixture,because the diffusion of carbon in ferrite is the rate-limiting step.Therefore,a higher temperature is required for the efficient decarburization of the thicker silicon steel sheet using the industrial continuous annealing production line. A mathematic model has been to predict the decarburization kinetics of grain-oriented silicon steel sheets in the gas mixture of N2-H2-H2O during annealing. This model is based on the carbon flux balance between the oxidation reaction at the surface and the carbon diffusion inside the steel sheet. It can be numerically solved to quantify the influences of annealing temperature and atmosphere on decarburization kinetics when the boundary conditions are properly determined. In case that a humid gas mixture is employed during annealing, the most influential process parameter is temperature rather than compositions of the gas mixture, because the diffusion of carbon in ferrite is rate-limiting step. wherefore, a higher temperature is required for the efficient decarburization of the thicker silicon steel sheet using the industrial continuous annealing production line.