Slope stability is a key issue in water conservancy projects，and its safety assessment is crucial to preventing landslides and protecting people's lives and properties.The traditional safety factor method cannot systematically consider uncertainty factors，and the obtained safety factor is a single value，which cannot accurately reflect the true safety status of the structure under different loads and environments.This study considers the spatial variability of the undrained shear strength of soft soil，proposes a stochastic limit analysis method for the reliability of soft soil slopes，and considers the impact of random distribution types on slope stability to reveal the soft soil under undrained conditions.Influence rules of soil slope reliability.The results show that the spatial variability of soft soil strength will significantly reduce the safety of the slope.The spatial variation parameters are used to conduct a reliability analysis of the unstable slope，and the grading method can ensure its safety.