A neutron capture therapy device comprising an accelerating tube for accelerating a proton beam, and a beam shaping assembly comprising: a proton beam inlet; a target arranged into the accelerating tube, wherein the target is adapted to have nuclear reaction with the incident proton beam from the beam inlet to produce neutrons, the neutrons forming a neutron beam; a moderator adjoining to the target, adapted to moderate the neutron beam to epithermal neutron energies; a reflector surrounding the moderator, wherein the reflector is adapted to lead deflected neutrons back to enhance epithermal neutron beam intensity; a thermal neutron absorber adjoining to the moderator, wherein the thermal neutron absorber is adapted to absorb the thermal neutrons 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 adapted to shield the leaking neutrons and photons so as to reduce the dose in non-radiation region; and a neutron beam outlet; wherein the accelerating tube includes an embedding portion embedded inside the moderator, the target being set at an end of the embedding portion, and an extending portion extending to an outer side of the moderator and being surrounded by the reflector; characterized in that the beam shaping assembly comprises a cooling system, wherein the cooling system comprises a first cooling part directly connecting with the target for cooling the target, a second cooling part and a third cooling part connecting with the first cooling part, the second cooling part and the third cooling part extending in a direction parallel to an axis of the accelerating tube respectively, and the cooling system configured to inputting a cooling medium into the first cooling part from the second cooling part and outputting the cooling medium from the first cooling part through the third cooling part; wherein the first cooling part is located between the target and the moderator, and the second cooling part and the third cooling part are located inside the beam shaping assembly and extend along a direction parallel to the axis of the accelerating tube to the outside of the embedding portion; and the first cooling part is located between the target and the moderator, whereby one side of the first cooling part connects with the target and the other side of the first cooling part connects with the moderator. a proton beam inlet; a target arranged into the accelerating tube, wherein the target is adapted to have nuclear reaction with the incident proton beam from the beam inlet to produce neutrons, the neutrons forming a neutron beam; a moderator adjoining to the target, adapted to moderate the neutron beam to epithermal neutron energies; a reflector surrounding the moderator, wherein the reflector is adapted to lead deflected neutrons back to enhance epithermal neutron beam intensity; a thermal neutron absorber adjoining to the moderator, wherein the thermal neutron absorber is adapted to absorb the thermal neutrons 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 adapted to shield the leaking neutrons and photons so as to reduce the dose in non-radiation region; and a neutron beam outlet; wherein the accelerating tube includes an embedding portion embedded inside the moderator, the target being set at an end of the embedding portion, and an extending portion extending to an outer side of the moderator and being surrounded by the reflector; characterized in that the beam shaping assembly comprises a cooling system, wherein the cooling system comprises a first cooling part directly connecting with the target for cooling the target, a second cooling part and a third cooling part connecting with the first cooling part, the second cooling part and the third cooling part extending in a direction parallel to an axis of the accelerating tube respectively, and the cooling system configured to inputting a cooling medium into the first cooling part from the second cooling part and outputting the cooling medium from the first cooling part through the third cooling part; wherein the first cooling part is located between the target and the moderator, and the second cooling part and the third cooling part are located inside the beam shaping assembly and extend along a direction parallel to the axis of the accelerating tube to the outside of the embedding portion; and the first cooling part is located between the target and the moderator, whereby one side of the first cooling part connects with the target and the other side of the first cooling part connects with the moderator.