With the Monte Carlo direct simulation method，we simulate the neutron tracks or histories by means of the random nature of the neutron interactions with the medium of shield which is a shell of the sphere made of Iron，and neutrons. are produced by the T(d，n)⁴He reaction with 300 keV deuteron beam energy. The reflective properties and absorptive properties of neutrons are analysed in the different thickness of the medium of Iron. These explanations and analyses of results have an important value in choosing shield parameters of spheric shell of fast neutron.