Approximate quantitative calculation method for estimated value of probabilistic security risk point

The invention provides a probabilistic safety risk point estimation value approximate quantitative calculation method, and belongs to the technical field of nuclear power plant safety analysis. The approximate quantitative calculation method for the estimated value of the probabilistic security risk point comprises the following steps: S1, acquiring FV importance degrees of a plurality of basic events, probabilities of the plurality of basic events and top event quantitative results corresponding to the plurality of basic events; s2, acquiring a linear slope of quantitative results of the basic event and the top event; and S3, constructing a relational expression between the changed basic event probability and the top event quantitative result, and calculating to obtain the changed top event quantitative result. When the probability of the basic event changes, the approximate point estimation value of the system fault tree top event can be quickly obtained by using the method, special PSA analysis software do