Abeam shaping assembly for neutron capture therapy includes a beam inlet, a target having nuclear reaction with an incident proton beam from the beam inlet to produce neutrons forming a neutron beam, a moderator adjoining to the target, a reflector surrounding the moderator. The neutrons are moderated to epithermal neutron energies by the moderator, and part of the moderator disposed on the back of the target can be replaced so as to adjust the epithermal neutron energies. The reflector leads the neutrons deviated from the main axis back.
