Up to now, ±800 kV ultra high voltage direct current(UHVDC) systems have the highest voltage level among existing DC systems in the world, thus the specification of the main equipments in the system's converter stations should be set carefully. Taking the system design and consultation of the Jinping-Sunan ± 800 kV UHVDC transmission project as an example, its specification of main equipments and key system technical parameters are presented and studied. The method of selecting parameters of station main equipment and the simulation result of system study are presented, in order to make a general description of ±800 kV UHVDC co system studies, such as system single line diagram (SLD) insulation margin, overload capability, transformer parameter, valve short current stress, and DC breaker study. As a result of the studies above, the surge arrester configuration of UHVDC system, insulation margin, overload capability, electrical design of valve and transformer had been given out in this paper. These specifications gave support to the development of equipment and construction of the project, and generalize experiences for future UHVDC project designs.