Abstract: The acoustic resonant scattering spectra of a porous sphere embedded in an elastic matrix is studied based on the resonant scattering theory proposed by Flax et al. Taking nodular cast iron as an example, some numerical computations are made for acoustic backscattering and resonant scattering spectra of certain partial waves. The change of acoustic resonance frequencies of different modes as a function of the porosity of porous spherical scatterers is also simulated. The numerical results show that the backscattering spectra change remarkably and the resonance peaks in the scattered partial waves of each order move to lower values with increasing porosity. Therefore experimental measurements of the backscattering spectra or resonance frequencies of the scattered partial waves may be used in evaluation of the porosity of spherical graphite in solid matrix.