Abstract: FAMS MC is a Monte Carlo program for correction on experimental measurement data of fast neutron energy spectrum.The corrections are carried out by FAMS MC program for secondary neutron double differential cross sections on 9Be induced by 5.9,6.4 and 14.1 MeV neutrons. The correction results by FAMS MC program are in good agreement with those calculated by MCNP program. The reliability of FAMS MC program has also been examined.