Abstract: The engineering property of the pebbly silty clay is difficult to determine accurately by the routine soil mechanics experiment because of its structure’s complexity.Depending on the Chuandong starch factory landslide,supported by the field test,the laboratory test and the project analogy method,this paper studies the determined method of the pebbly silty clay’s shear strength etc inderes,discusses the formation mechanism,the controlling factors and the geological model,and analysises on the stability under the current situation,the rainstorm and the water level dynamic variationsin after water storage of three gorges reservoir etc environmental conditions by the limit equilibrium theory.At the same time,the sensitivity analysis of shear strength parameters in pebbly silty clay stability is studied.