Strength property of slip zone soils has important control action for slope stability. It is essential premise that revealing the variation law of strength indices for slope stability analysis. Aiming at an ancient landslide in reservoir area

the experimental study of shear strength of fine-grained soil containing coarse-grains in sliding zone was carried out. Based on large-scale field shear test and laboratory consolidated quick shear test

the shear characters of slip zone soils were compared; and the strength indices were defined by field recycled strength

field reduction strength

and consolidated quick shear strength in laboratory. For the deficiencies of repeated direct shear test in fine-grained soil containing coarse-grains

the improvement of test process and examination apparatus has been carried out; and the reasonability of test result was verified. Basis of the statistic rule of test data

the influence of moisture content

plasticity index

and coarse-grained content on strength indices has been discussed; the shear property distinctness between fine-grained soil containing coarse-grains and clay or sand was summarized.