Abstract: The reliability of UHV AC switch-gear and bushing during its whole life cycle has always been a major concern of Power Grid Corp and equipment manufacturers. The study of long term live test is the key to ensure the safety and stable operation of the large power grid. In this paper, the technical parameters of main test equipment, impedance calculation of the 1100kV/10kA test loop and the design of the auxiliary grounding grid are described in detail. As the GIS shell of the 1100kV/10kA power current transformer has no external circulation channel, a special designed copper grounding grid is designed and it's current carrying capacity, power loss, voltage drop are calculated and verified. Meanwhile, shunt capacitor are installed at both ends of the power current transformer, which compensated the inductive reactive power of the test loop, reduced the section of the winding and the power capacity requirement. Finally, the expected research work of the AC long term live test loop in future is briefly introduced.