The invention provides a device for globally enhancing the field intensity of a large-scale effector in an irradiation cavity, so that the field intensity of a large-scale region in the large-scale effector is improved, and the effect of globally enhancing the internal measuring point field of the large-scale effector is achieved. According to the device, on the basis that the decrease of the distance between an upper flat plate and a lower flat plate of a working space of the irradiation cavity can increase the field intensity of the working space, and electromagnetic wave can generate reflection and refraction theory on the surface of medium, when a global enhancement mode of the internal field intensity of the large-scale effector in the irradiation cavity is studied, it is found that when a medium block with a certain size, shape and medium parameters placed in a metal plate which works under the irradiation cavity, the effector placed on the medium block, and a medium sleeve addedinto the effector are adopted, the field in the large-scale effector has a globally enhanced phenomenon, and the effect of enhancing the field intensity is partly better than the conventional means that the distance between the upper flat plate and the lower flat plate of the working space of the irradiation cavity is reduced, and the voltage peak value of an excitation source of the irradiationcavity is increased.