A radiation irradiation system includes a radiation irradiation device and a treatment bed for transporting a target to be irradiated, the treatment bed has a positioning assembly. The positioning assembly includes a shielding body and a sealing bag for accommodating the shielding body. The shielding body includes silicone and a radiation shielding material which is capable of shielding radiation. After the positioning assembly with the target to be irradiated is placed on the surface of the sealing bag is vacuumized, the positioning assembly is recessed with a shape of the target to at the position where the target to be irradiated is placed and forms a contour as the target to position the target. The positioning assembly is provided to position the target to avoid therapeutic effect caused by the movement of the target during the irradiation therapy, and avoid radioactive damages to the target except for the parts on which irradiation therapy needs to be performed, and to medical staff during the radiation irradiation therapy.
