Wustite-based catalyst for ammonia synthesis exhibits extremely high activity and easy to reduction under a wide range of conditions. The reaction kinetics of ammonia synthesis can be illustrated perfectly by both the classical Temkin-Pyzhev and modified Temkin equations with optimized alpha of 0.5. The pre-exponent factors and activation energies at the pressures of 8.0 and 15.0 MPa are respectively k(0) = 1.09 x 10(15), 7.35 x 10(14) Pa(0.5)(.)s(-1), and E = 156.6, 155.5 kJ(.)mol(-1) derived from the classical Temkin-Phyzhev equation, as well as k(0) = 2.45 x 10(14), 1.83 x 10(14) Pa(0.5)(.)s(-1), and E = 147.7, 147.2 kJ(.)mol(-1) derived from the modified Temkin equation. Although the degree of reduction under isothermal condition is primarily dependent upon temperature, low pressure seems to be imperative for reduction under high temperature and low space velocity to be considered as a high activity catalyst. The reduction behavior with dry feed gas can be illustrated perfectly by the shrinking-sphere-particle model, by which the reduction-rate constants of 4248exp (-71680/RT) and 644exp (-87260/RT) were obtained for the powder (0.045-0.054 mm) and irregular shape (nominal diameter 3.17 mm) catalysts respectively. The significant effect of particle size on reduction rate was observed, therefore, it is important to take into account the influence of particle size on reduction for the optimization of reduction process in industry.