Abstract: It is studied 2～18GHz electromagnetic properties of light-burned calc-lime and light-burned magn-lime and its changing rule.In 2～18GHz microwave frequency,real permittivity of light-burned calc-lime is a little bigger than that of light-burned magn-lime,their real permeability is almost equal to one.Their dielectric loss angle tangent and magnetic loss angle tangent are small;furthermore,these two values are almost the same.Especially at frequency 2.45GHz,the values of dielectric loss angle tangent,magnetic loss angle tangent and conductance of light-burned calc-lime are all bigger than those of light-burned magn-lime,which indicate microwave absorption of light-burned calc-lime is comparatively better and it is fit for heating process in microwave metallurgy.