Abstract: The research concerns in the moderating characteristics analysis of Al, Al₂O₃ and AlF₃ placed in the neutron beam passage of Tsinghua University experimental reactor by Monte-Carlo method. The main moderating performances of above 3 kinds of materials used in constructing epithermal neutron radiation field are obtained, and the optimized moderating material, an Al-AlF₃ mixture with a mass fraction ratio w(Al)/w(AlF_3⁾of 2/3, is recommended for Tsinghua University experimental reactor.