Based on the case study of external Qinhuai River dike a numerical study on the seepage stability and slide stability was carried out while considering the geomembrane placed on upstream face of the dike. The stability analysis were simulated with geomembrane under the design-flood-level and rapid-drawdown operating conditions. Especially under the latter operating condition

a simulation considering three hydraulic conductivity’s calculating schemes was carried out in the whole process of the rapid drawdown. According to these analyses

a basic safety evaluation related to the external Qinhuai River dike was made

and some helpful conclusions were illustrated between the stability of dike and geomembrane placed on upstream face. The analysis method and the results will be practical and helpful in dike engineering practice.