A beam shaping assembly (10) used in a neutron capture system and capable of changing an irradiation range of a neutron beam. The beam shaping assembly comprises: a beam inlet (11), a target (12), a moderator (13) adjoining the target (12), a reflector (14) surrounding the moderator (13), a thermal neutron absorber (15) adjoining the moderator (13), a radiation shield (16) arranged inside the beam shaping assembly (10), and a beam outlet (17). The target (12) has a nuclear reaction with an incident proton beam from the beam inlet (11) to produce neutrons, the neutrons form a neutron beam, and the neutron beam defines a main axis (X)； the moderator (13) moderates the neutrons produced from the target (12) to an epithermal neutron energy range； the reflector (14) leads the neutrons deviated from the main axis (X) back to the main axis (X) so as to achieve the effect of converging epithermal neutrons； the thermal neutron absorber (15) is used for absorbing thermal neutrons to avoid overdosing in superficial normal tissue during therapy； the radiation shield (16) is used for shielding leaking neutrons and photons, so as to reduce the dose of the normal tissue of a non-irradiated area； and the beam shaping assembly (10) further comprises replacement components (21, 22) that can be attached to and detached from the beam shaping assembly (10) to change the irradiation range of the neutron beam.La présente invention concerne un ensemble de mise en forme de faisceau (10) utilisé dans un système de capture de neutrons et capable de modifier une plage d'irradiation d'un faisceau de neutrons. L'ensemble de mise en forme de faisceau comprend : une entrée de faisceau (11), une cible (12), un modérateur (13) adjacent à la cible (12), un réflecteur (14) entourant le modérateur (13), un absorbeur de neutrons thermiques (15) adjacent au modérateur (13), un écran anti-rayonnement (16) disposé à l'intérieur de l'ensemble de mise en forme de faisceau (10), et une sortie de faisceau (17)
