Abstract: The Jinpingzi landslide is a typical creep landslide with total volume of about 6.25×10⁸ m³ on the right bank of the Jinsha River, about 900 m from dam of Wudongde hydropower Station. This paper further clarifies the internal mechanism controlling the activity pattern of the landslide, the characteristics of residual strength and the peak strength of slip zone. It provides references for the protection and management of similar landslides. It employs a series of repeated shear tests under different clay contents. It is found that the strain-softening phenomenon of sliding zone soil is becoming more obvious as clay content increases. The residual strength and peak strength of sliding zone soil show a nonlinear decrease law as clay content increases, but the decreased degree increases as normal stress increases. Meanwhile, the residual internal friction angle and peak internal friction angle have a good linear negative correlation with the clay content. The peak cohesion and residual cohesion increase as clay content increases, but there is a decrease at clay content 40%. The reason for the decreasing tendency of the cohesion may be that the distribution of bound water around the clay particles has a critical effect on the strength characteristics of the slip zone, especially for the cohesion. Data and results of this paper have important significance to the protection and management of Jingpingzi landslide and the evolution process of creep landslides under different particle sizes.