Perfluoroisobutyronitrile(C4F7N) is considered to be the most potential alternative gas for SF6 due to its excellent dielectric strength but lower effect on global warming for atmospheric environment. For the large usage of SF6 in UHV GIL, it is urgent to develop UHVeco-friendly GIL with C4F7N gas. The key Characteristics of GIL design including insulation performance and gas-solid compatibility were investigated in this paper. And the key parameters were provided for 9% C4F7N/91% CO2 mixture with the filling pressure of 0.7 MPa, as well as the critical electric field values for GIL insulation design. The simulation analysis of insulation, thermal, strength and sealing design were performed for UHV eco-friendly GIL. A standard line unit prototype was manufactured with the dielectric medium of 9% C4F7N/91% CO2 mixture and passed the complete type tests. The eco-friendly GIL prototype was conducted by the live test at UHV AC test base in Wuhan. The results from partial discharge monitoring and gas states measurement have shown that UHV eco-friendly GIL is with good operation condition.