Numerous studies on the instability and shear strength of expansive soil slopes have suggested that the fundamental reason forshallow sliding failures is insufficient shear strength caused by repeated dry-wet cycles under low stress. Therefore, this paper studiedthe effects of low stress and dry-wet cycles on the shear strength of expansive soil slopes. A nonlinear curve that can be well fittedusing generalized power functions was observed for the shear strength of expansive soil, and a numerical model with nonlinearlydistributed shear strength taken into consideration was built using FISH. In this way, the dynamic distribution of shear strength as afunction of vertical stress was obtained. Compared to conventional models, the proposed model was more accurate in terms oftheoretical aspects, and the obtained results exhibited improved consistency with the actual mode. In order to improve theapplicability of this model, a mapping model of atmospheric action and engineering design of safety factors of slopes was establishedusing a Gaussian Process Regression (GPR) model, which is suitable for cases characterized by high dimension, small samplepopulation, and nonlinearity. Herein, the numerical calculations were replaced with output responses. In this way, fast prediction ofthe stability of expansive soil slopes in terms of a shallow sliding failure prediction model was achieved. To verify the feasibility ofthe proposed approach, dynamic predictions of shallow sliding failures of expansive soil slopes were carried out for NanyouHighway under different rainfall conditions. Meanwhile, safety factor responses corresponding to different slope design schemeswere also obtained using the proposed model, providing reference for slope stability analysis in expansive soil zones.