Abstract: The feedback analysis of anti-seepage behavior of composite geomembrane is performed based on nearly 20 years of seepage monitoring data from Wangfuzhou hydraulic project. Firstly, the qualitative analysis of the overall seepage behavior of the embankment earth-rock dam is carried out. Then a typical section is selected to establish the statistical model of piezometric level for quantitative analysis. Subsequently, the orthogonal design, neural network and numerical method are combined to invert the permeability coefficient of the composite geomembrane. Finally, the work behavior of the composite geomembrane is analyzed comprehensively. The results show that the piezometric level only changes greatly at the initial stage of water storage and operation, and the change is relatively stable at present. Additionally, it is found that the piezometric level and separated time-dependent components of three piezometers in the typical GY5 section decrease gradually. At the same time, the permeability coefficient of the composite geomembrane inverted by the piezometric level is 1.11×10^-10 cm/s. The comprehensive analysis shows that the composite geomembrane of Wangfuzhou hydraulic project still has good anti-seepage behavior after nearly 20 years of service, and there is no obvious aging trend.