Based on transient analysis,stress value and values of principal stress of slope can be got at each time. Then based on partial failure discriminance, the only slip plane can be got to some initial point. Thirdly, based on sweden slice method, formula of the safety coefficient of the slope's stability can be as objective function, through artificial fish-swarm algorithm, slip plane can be established. Finally, through analyzing the safety coefficient of the slope's stability and initial point in each time, the structure reliability of slope stability and failure probability can be got. Finally, this method is verified by an example, which proved that the method is feasible and available.