Disclosed is a beam shaping assembly for neutron capture therapy, including a beam inlet； a target, wherein the target has nuclear reaction with the incident proton beam from the beam inlet to produce neutrons； a moderator adjoining to the target, wherein the neutrons are moderated by the moderator to epithermal neutrons； a reflector surrounding the moderator, wherein the reflector leads the deflected neutrons back to the moderator to enhance the epithermal neutron beam intensity； a thermal neutron absorber adjoining to the moderator, wherein the thermal neutron absorber is used for absorbing the thermal neutron so as to avoid overdosing in superficial normal tissue during therapy； a radiation shield set inside the beam shaping assembly, wherein the radiation shield is used for shielding the leaking neutrons and photons so as to reduce the dose in non-radiation region； a beam outlet； and a cooling system, wherein the cooling system includes a first cooling part for cooling target, a second cooling part and a third cooling part connecting with the first cooling part and extending in a direction parallel to the axis of the accelerating tube respectively, the first cooling part connects with the target in a face to face manner, the cooling medium is inputted into the first cooling part from the second cooling part and is outputted from the first cooling part through the third cooling part.
