Abstract: The standard spectrum was recommended in the ISO 8529-1 according to PTB experimental measurements for Am-Be neutron source. In order to verify its universality, the processes of neutron production for the PTB ISO source and a China-made source were theoretically calculated and simulated by Monte-Carlo method. The detailed influences from different manufacturing parameters on physical characteristics of sources, such as neutron spectrum, average neutron energy, fraction of neutrons below 1.5 MeV, source strength, 4.438 MeV γ-ray to total neutron ratio and emission anisotropy were discussed and reviewed.