Considering the frequent breakage of the hard jumper shield ring in the strain tower of ultra-high voltage alternating current 1000 kV Nan-Jing Transmission Line, the theoretical and experimental studies on new shield ring were carried out in terms of mechanical properties; however, due to the structural changes of shield ring, the field characteristics should be calculated and analyzed. In accordance with the theory that there is no electric field in a metal conductor under electrostatic equilibrium, if there is any metal conductor in the 3D model of the computational domain, there will be no need to subdivide the metal conductor. In this paper, a 3D model load applying method with metal conductors was proposed to calculate the field intensity of Tuned mass damper (TMD) shield ring after improving the mechanical properties of the strain tower, which saved the total number of mesh subdivisions by 48.02%, reduced the computational time by 76.47%, and increased the computational efficiency of 3D numerical electric field. The calculation results validated the correctness and effectiveness of this method. The new TMD shield ring with the field intensity meeting the relevant requirements was adopted in 1000 kV Nan-Jing Loop Transmission Line in December 2016, which has been operating in good condition so far.