Abstract: With the use of best estimate computer code of pressurized water reactor (PWR) severe accident, the impact of different pressurizer surge line creep rupture failure sizes on severe accident progress and results was studied. Calculation results show that equivalent diameter of pressurizer surge line creep rupture failure at 15 cm will receive a relatively conservative result, however, when the failure size is under 12 cm or beyond 18 cm, the calculation results are not as serious as 15 cm case. The results can be used as reference for further studying severe accident phenomena in a typical PWR nuclear power plant．