Taking the high earth-rock cofferdam project based on the deep overburden as an example, the sensitivity of the seepage field to the permeability coefficient of the layer of soil, the bedrock and the concrete cut-off wall is analyzed by using the finite element method. The sensitivity of the seepage field of cofferdam to the permeability coefficient of these materials is discussed. The results show that the greater the permeability coefficient of the layer of soil, the bedrock and the concrete cut-off wall is, the higher exit-point the downstream slope of the cofferdam has, the larger the single width seepage of the cofferdam and its foundation is and the greater the maximum penetration gradient is . Therefore, for the high earth-rock dam cofferdam project, the permeability coefficient of the deep overburden, the layer of soil, the bedrock and the concrete cut-off wall have a significant influence on its seepage field, and should be determined as reasonably as possible in the engineering survey and design process, so that a reliable basis can be provided to cofferdam stability analysis through accurately and reasonably determining the cofferdam and its foundation seepage field.