Modelling of an industrial catalytic ammonia oxidation reactor for nitric oxide production in nitric acid plant over gauzes of Pt/Rh catalyst presents the current study. Two basic models for mass balance and energy balance were used (after integration by matlab 2017) for an industrial ammonia oxidation reactor. The first model (mass balance) was used to predict the variation of the concentration of N,, NO and O along the catalyst bed of the reactor (4.8m diameter, 1m height). The second model (energy balance) was used for the same reactor to predict temperature variation along the catalyst bed. The deviation in the 1st case didn't exceed 6.2 % (for NO). Also in case of energy balance the deviation was 0.4 %, so the mathematical models have shown quite high degree of accuracy to predict the operating values with minimum deviation. The rate of consumption/ formation for N,, NO and O were also calculated.