Abstract: In order to improve the reliability and safety of the UHV transmission system,the simulation model of 1,000 kV typical transmission system is established by using EMTP,the overvoltage of the neutral point small reactance under the power frequency,operation or lightning overvoltage condition are calculated and analyzed in this paper. And the suppression effect of shunt reactor and metal oxide arrester on overvoltage is studied. The overvoltage of neutral point small reactance of shunt reactor is analyzed emphatically and its insulation level is checked and calculated. The experiments have found that the shunt reactor can effectively suppress the power frequency overvoltage on the line and small reactance,and the lightning arrester can effectively limit the operating overvoltage and the serious overvoltage during the three-phase reclosing process.The rated voltage of the neutral point arrester is recommended to be 180 kV or 192 kV. The insulation level can be selected as:550 Kv for the lightning impulse withstand voltage and 230 kV for the short-time power frequency withstand voltage.