The effects of urea molar ratio (1.0 - 2.0), reaction temperature and additives on NO reduction in flue gas have be en determined ina pilot-scale flow reactor. A kinetic model is proposed for NO reduction rare with -NH and -CN in selective reducing agents (urea, cyanuric acid, ammonia). Two primary reactions can be expressed kinetically in the DeNO(x) profess as : N.S. (nitrogenous species) + O-x (oxidants)-->NO + ...(k(i); rate constant for NO formation) N.S. + NO-->N-2 + ... (k(r); rate constant for NO reduction) in which the rate constants of k(f) and k(r) in the model are determined from the experimental data in the temperature range 1173 K - 1373 Ii as : k(f) = 4.01 x 10(11) esp (-267/RT) k(r) = 7.24 x 10(10) exp (-230/RT) The proposed model can predict the lowered activation energies caused by the addition of different species and molar ratio to NO.