It was experimentally found that the app Ea and reaction order varied significantly even in the reaction conditions commonly used in the literature, not only for Fe-based catalysts but also for Ru-based catalysts. The reason why app Ea and reaction order change with experimental conditions can be explained by the coverage. The Coverage can be obtained by kinetic analysis of the reaction rate of ammonia synthesis without using experimental techniques such as chemisorption. Adding K to Ru changes the coverage, and the method presented in this study can be used with K-doped systems, which are more commonly used in industrial processes.