The invention relates to a novel full-sealed electromagnetic shielding impedance box. The novel full-sealed electromagnetic shielding impedance box comprises a box body and a foundation, wherein the outer side of the foundation is respectively provided with a grounding end, a foundation outer side measurement end coaxial cable jack and a foundation outer side signal end coaxial cable jack in a circumference direction, the box body comprises an electric field shielding cover and a magnetic field shielding cover which are sleeved with an interval, the electric field shielding cover is arranged at the outer side of the magnetic field shielding cover, intervals are arranged between the top portion and circumference of the magnetic field shielding cover and the electric field shielding cover, and bottom portions of the electric field shielding cover and the magnetic field shielding cover are respectively provided with an opening. The method is more applicable to AC high voltage signal measurement in complex on-site test environments and can realize long-time measurement without influence of external factors such as, an electromagnetic environment, rain, snow, dust storm, on-site wiring and disposing position.