The measured pulse amplitude distributions of recoil protons and electrons were converted to
neutron energy or gamma energy spectra by double differentiation (Toms, 1971) or matrix conversion methods respectively. The results of neutron spectra measured behind different thicknesses of hematite-serpentine and ilmenitelimonite concrete shields are displayed respectively. The obtained spectra in these two figures show that the flux intensity decreases with the increasing of the concrete thickness for all energies.