Precondition subset simulation method for efficiently calculating groundwater pollution failure probability

The invention discloses a precondition subset simulation method for efficiently calculating groundwater pollution failure probability. The precondition subset simulation method comprises the following steps: generating N underground aquifer Gaussian permeability coefficient fields through sequential Gaussian; respectively substituting the Gaussian permeability coefficient fields of the N underground aquifers into a performance function of an underground water pollutant migration model to calculate response values; arranging the response values according to an ascending order to obtain a seed sample and a threshold value; taking the seed sample as an initial sample of each Markov chain, and generating a candidate sample according to a precondition Klankningelson technology; judging whether the candidate samples are within a failure threshold, accepting the candidate samples falling within the failure threshold, and rejecting the candidate samples falling outside the failure threshold; and repeating the Markov