Abstract: The Tiantaixiang landslide is one of the typical gently dipping translational rock slides forming in the red beds in east Sichuan province. In order to discover the mechanism of these landslides, the slip zone behavior of Tiantaixiang landslide is studied in detail. Physical property tests show that the slip zone soil is plastic silty clay. The X-ray diffraction analysis reveals that the main mineral components of the slip zone are composed of chlorite, illite, feldspar, quartz and calcite. The results of scanning electron micrograph display that the microstructures of the slip zone are mainly sheet crystals and directional crystal structures, and micro pores developed well. Consolidated slow direct shear tests are conducted on the slip zone specimens. The results are c=9.2~10.7kPa and ＝10.4~12.3.Triaxial consolidated drained creep tests are conducted on the slip zone specimens to obtain the creep strength. The results show that the creep strength are c=18.1kPa and ＝8.0.The large amount of chlorite and illite in the slip zone resulting in low shear strength and low creep strength is the main inner factor contributing to the sliding.