Soil slopes under different stability，the displacement will be different，while the impact of slope displacement factors are more，and then make its changing trend is complex.In order to obtain the relationship between slope displacement and stability，BP neural network algorithm and strength reduction method are used to predict the safety factor of soil slope.The results show that the slope displacement is calculated by the strength reduction method and the BP neural network sample data is obtained.When the number of iterations is enough，the error between the prediction result and the actual result can be neglected.Through the slope monitoring in the actual project data，and then by the establishment of the BP neural network can be more accurate output slope strength reduction factor，and then get the corresponding safety factor.