Abstract: Level 2 Probabilistic Safety Analysis (PSA) can be used to quantitatively assess the risk of severe accident and is a good tool to evaluate the severe accident management. By studying the general method and procedure for the application of level 2 PSA in severe accident management, taking an improved generation-Ⅱnuclear power plant as an example, the “primary loop depressurization operation ” and the “ primary loop emergency water injection” in severe accident management guideline are quantitatively evaluated. Analysis shows that performing the “primary loop depressurization operation” immediately after entering the severe accident management guideline can greatly reduce the risk of large radioactive release, and performing “primary loop emergency water injection operation” contributes greatly to reducing the risk of large radioactive release in the slower accident sequence. The study shows that there still has further improvement room in severe accidents management for nuclear power plants in China.