The present disclosure provides a neutron capture therapy system including a beam shaping assembly. The beam shaping assembly includes a beam inlet a neutron generator arranged into the beam shaping assembly, the neutron generator has nuclear reaction with an incident proton beam from the beam inlet to produce neutrons a moderator adjacent to the neutron generator, the neutrons are moderated by the moderator to epithermal neutron energies a reflector surrounding the neutron generator and the moderator, the reflector leads the deflected neutrons back to enhance epithermal neutron beam intensity a beam outlet and at least a movable member moving away from or close to the neutron generator, wherein the movable member moves between a first position and a second position, when the movable member is at the first position, the neutron generator is replaceable and when the movable member is at the second position, the neutron generator is irreplaceable. The neutron generator is easy to be replaced. The neutron capture therapy system has a simple structure, and is flexible to use.
