An inverse method for retrieving absorption and scattering coefficients of nanoporous thermal insulation is proposed on the basis of a modified two flux method for solving radiative transfer, a genetic algorithm based global identification method, and normal-hemispherical reflectance and transmittance measurements. First, the inverse method is numerically validated by using radiative properties of two types of glass reported in the literature. Then, the normal-hemispherical reflectance and transmittance of nanoporous thermal insulation are measured, and the absorption and scattering coefficients of the material at wavelength between 0.4 μm and 7.0 μm are retrieved. The results show that (1) the proposed inverse method is able to retrieve accurately the absorption and scattering coefficients of nanoporous thermal insulation； (2) for wavelength of 0.4—7.0 μm, the retrieved absorption coefficient is ranging from 70m^-1 to 3 900 m^-1, while the scattering coefficient is between 180m^-1 and 3 000 m^-1, the values vary in a wide range for different wavelengths, and a strong spectral selectivity can be observed； and (3) for wavelength below 2.5 μm, the fraction of scattering is larger than those for absorption, while absorption dominates for wavelength larger than 2.5 μm, the material featuring strong absorption and weak scattering.