A beam shaping assembly (10, 20, 30, 40, 50) for neutron capture therapy comprising: a beam inlet (11, 21, 31, 41, 51); a target (12, 22, 32, 42, 52), configured such that the target has a nuclear reaction with an incident proton beam from the beam inlet to produce neutrons, and wherein the neutrons form a neutron beam defining a main axis (X, X1, X2, X3); a moderator (13, 23, 33, 43, 53) adjoining to the target, configured such that the neutrons are moderated by the moderator to epithermal neutron energies, the material of the moderator has been prepared from a material containing at least one of LiF, Li 2 CO 3, Al 2 O 3, AlF 3, CaF 2 and MgF 2; a reflector (14, 24, 34, 44, 54) surrounding the moderator, configured such that the reflector leads the neutrons deviated from the main axis back to enhance epithermal neutron beam intensity; a thermal neutron absorber (15, 25, 35, 45, 55) adjoining to the moderator, wherein the thermal neutron absorber, when in use, is used for absorbing thermal neutrons so as to avoid overdosing in superficial normal tissue during therapy; a radiation shield (16, 26, 36, 46, 56) arranged inside the beam shaping assembly, wherein the radiation shield is configured for shielding leaking neutrons and photons so as to reduce dose of the normal tissue not exposed to irradiation; and a beam outlet (17, 27, 37, 47, 57), characterized in that the material of the moderator has been subjected to a powder sintering device (100, 200) so as to change powders or powder compacts (107, 204) into blocks; and the material of the moderator has been prepared by mixing a mixture containing one or more of PbF 4, Al 2 O 3, AlF 3, CaF 2 and MgF 2 and a 6 Li element-containing material accounting for 0.1 to 5% in percentage by weight of the mixture. a beam inlet (11, 21, 31, 41, 51); a target (12, 22, 32, 42, 52), configured such that the target has a nuclear reaction with an incident proton beam from the beam inlet to produce neutrons, and wherein the neutrons form a neutron beam defining a main axis (X, X1, X2, X3); a moderator (13, 23, 33, 43, 53) adjoining to the target, configured such that the neutrons are moderated by the moderator to epithermal neutron energies, the material of the moderator has been prepared from a material containing at least one of LiF, Li 2 CO 3, Al 2 O 3, AlF 3, CaF 2 and MgF 2; a reflector (14, 24, 34, 44, 54) surrounding the moderator, configured such that the reflector leads the neutrons deviated from the main axis back to enhance epithermal neutron beam intensity; a thermal neutron absorber (15, 25, 35, 45, 55) adjoining to the moderator, wherein the thermal neutron absorber, when in use, is used for absorbing thermal neutrons so as to avoid overdosing in superficial normal tissue during therapy; a radiation shield (16, 26, 36, 46, 56) arranged inside the beam shaping assembly, wherein the radiation shield is configured for shielding leaking neutrons and photons so as to reduce dose of the normal tissue not exposed to irradiation; and a beam outlet (17, 27, 37, 47, 57), characterized in that the material of the moderator has been subjected to a powder sintering device (100, 200) so as to change powders or powder compacts (107, 204) into blocks; and the material of the moderator has been prepared by mixing a mixture containing one or more of PbF 4, Al 2 O 3, AlF 3, CaF 2 and MgF 2 and a 6 Li element-containing material accounting for 0.1 to 5% in percentage by weight of the mixture.