The voltage source converter based high voltage direct current transmission (VSC-HVDC) project has entered the era of ultra-high voltage (UHV). Electric field equalizing design of the existing VSC valve cannot meet the requirement of UHV. In order to reduce the electric field density of the top tubular busbar of ±800 kV VSC valve, the modeling technologies of PTC Creo and ANSYS are applied for the three-dimention complex valve tower modeling to analyze electrostatic field finite elements. By adding a top shield plate equalizing connected with the top tubular busbar, the peak electric field densities of the top sub modules and tubular busbar are reduced obviously. The parasitic capacitance parameters of the valve tower are extracted. The influence of the top shield plate on the voltage distribution of sub-modules under the switching impulse is analyzed. The influence of distance among electric field equalizing parts on the distribution of peakelectric field is studied. The optimal electric field equalizing design of ±800 kV VSC valve is obtained, and the experiment of impulse voltageon valve tower prototype is tested. The proposed optimization measurement improves the stable operation of VSC valve in UHV application, and provides a design reference for the application of VSC valve in subsequent UHV VSC-HVDC projects.