Two methods are widely used to represent the microwave absorption properties of ceramics: measuring the values of electromagnetic parameters such as permeability and permittivity, or directly measuring the reflection rate of a metal-backed slab sample made of this material. However, do these two methods coincide with each other? If not, which method should be used as right way to represent this kind of ceramics? To answer these questions, both methods are carried out on the same ceramics, of which the results are compared. Distinct difference between these measured results is found, and the possible reasons for the difference are also discussed.