A plug flow tubular reactor model for the oxidation of methanol in a fixed-bed reactor over silver catalyst has been presented in this paper. The model performs the dynamic behavior for the oxidation reaction of methanol and formaldehyde throughout the reactor length. The literature data are used to validate the model accuracy. The effect of time and the amount of water in feed are studied in the simulation study. The model gives the acceptable prediction of the formaldehyde yield, especially at rea