Abstract: In this paper, taking the creep instability slope of Aleshan Opencast Coal Mine as an example, the triaxial shear test was carried out in laboratory to obtain the strain laws of the sliding belt soil samples under different confining pressures and stresses, and the isochronous curve method was further used to determine the long-term strength of the sliding belt soil. The study shows that the interlayer thin strip soil has typical creep characteristics, and the creep stage can be divided into two deformation processes: the attenuated creep and the stable creep. The absolute creep and the deformation rate of the stable creep stage are all positively correlated with the axial stress value, while the duration of the creep stage increases with the shear stress level. There is a linear increase. The long-term strength of the sliding zone soil is less than that of the same condition. Compared with the conventional strength parameters, the long-term cohesive C value and the long-term friction angle of the soil decreased by 24.8% and 22.4% respectively.