A neutron moderation material for use in a BNCT beam shaping assembly. The neutron moderation material comprises three elements, i.e., Mg, Al, and F, wherein the mass fraction of the Mg element is 3.5%-37.1%, the mass fraction of the Al element is 5%-90.4%, and the mass fraction of the F element is 5.8%-67.2%； the sum of the weights of the Mg, Al, and F elements is 100% of the total weight of the neutron moderation material. The neutron moderation material may be doped with a small amount of 6 Li-containing substances, and the addition of the 6 Li-containing substances effectively decreases the content of ³-rays in epithermal neutron beams.
