The measured results of ε_r and μ_r of 4 radar absorbing materials is given, and a comparison between the optimizing calculated value of electric properties and the measured value is made, electric properties of radar absorbing materials evaluted by means of measured results of ε_r and μ_r is discussed. The investigation shows that there is a certain difference between the calculated results and the measured results, among them, the dispersion effect and measuring accuracy influences significantly optimizing calculated results of electric properties.