Abstract: Using the theory of electromagnetic wave transmission,the reflectivity formulas at the oblique incident electromagnetic wave were studied and deduced. And the relationship between the reflectivity, the various electromagnetic parameters, isolation layer thickness and incident wave frequency were discussed by means of using the 3D mesh method. The results indicated that the incidence angle has a great influence on the reflectivity in the range of 2~18 GHz. In the case of f=16 GHz, the increase of the μ_r1 and μ_r2 values of the material makes the magnetic loss and energy storage capacity of the material increase, which results in a good absorption effect. However, when the ε_r1 and ε_r2 values of the material, due to the surface reflection effect, the absorption effect is decreased. The reflectivity can reach up to 4.5 dB after the 2~18 GHz band, which can meet the military and civil requirements.