In order to search for the effective laser interfering techniques,foam as a new passive photo-electricity interfering medium was studied.Using the Mie scattering theory,the relationships among mass extinction coefficients (MEC) of foam and the several important parameters of foam itself in two military laser wavelengths (1.06μm and 10.6μm) were calculated and analyzed.From the results of calculation and analysis,it shows that different wavelength and different refractive index have different condition.These results of study can provide the tactics application of foam with necessary theoretical basis.