Abstract: Sand-mudstone interbedded frock mass presents a typical complex geological condition, with a highly intricate seepage field distribution. Traditional seepage control analysis methods are difficult to accurately describe the behavior of the seepage field. Based on the innovative calculation method of the equivalent seepage field in the sand mudstone interlayer foundation, this study revealed the distribution pattern of the equivalent seepage field in the sand-mudstone interbedded foundation and the influence of different seepage control schemes on it. It proposed a calculation method for the equivalent seepage field of sand and mudstone interlayer foundation based on the structural characteristics of sand and mudstone interlayer foundation and the layered seepage of soil. Building upon this, a three-dimensional finite element seepage field computational model was developed for Puhua reservoir project, which incorporates the geological conditions, layout of the structure, and seepage control measures. The study investigated the influence of the permeability anisotropy of the sand-mudstone interbedded foundation on the seepage field, and analyzed the effects of different combinations of depths and lengths of impermeable curtains on the seepage flow and seepage gradient of the surrounding rock masses. The results show that when the permeable layer is not completely intercepted by the curtain, increasing the depth of the impermeable curtain can significantly reduce the seepage flow in the dam foundation and both abutment rock masses. Deepening the impermeable curtain reduces the seepage gradient at the seepage outflow point of the abutment rock masses while increasing the seepage gradient at the dam foundation and the impermeable curtain. Lengthening the impermeable curtain can reduce the seepage flow and seepage gradient of both abutment rock masses. Increasing the curtain length primarily affects the seepage flow field on the side where the curtain is extended, but further improvements in seepage control become less significant as the curtain lengthens. The seepage of sand-mudstone interbedded foundation exhibits anisotropic characteristics, and the seepage flow of the foundation can be effectively controlled by setting a reasonable depth and length of anti-seepage curtain. This study provides valuable insights for selecting seepage control measures on sand-mudstone interbedded foundations.