Existing data has indicated that the seepage amount in the dam is inversely proportional to the temperature. Higher temperatures result in less seepage, while lower temperatures lead to more seepage. Seepage mainly occurs in the U3 section of the Wanyao Reservoir, and the effects of several anti-seepage measures have not been very significant. Since the seepage channel in the U3 section directly leads to the gallery in the front of the dam and is closely related to the reservoir water level, the impact of the current water level on seepage can be considered significant, and the lag effect of the water level on seepage can be ignored. Therefore, considering the frequent occurrence of extreme weather in recent years, such as high temperatures in summer and freezing conditions in winter, which can have a significant impact on existing seepage channels in the dam and even pose safety hazards, it is necessary to study the seepage amount of the Wanyao Reservoir under conditions of high water level and low temperature.Temperature was calculated using the Cubic Law, an analytical expression for the size of the seepage channel in the U3 section, and the relationship between temperature and measured seepage amount. A three-dimensional groundwater flow numerical model was established using COMSOL software. The model parameters were identified and validated using the measured water level data, and the seepage amount of the dam under different operating conditions was predicted. The model parameter inversion results show that, with the exception of a relative error of 1.53% in the U504 hole, the relative errors in the other observation holes are all less than 1%, indicating that the model has a good overall fit to the observation data. The model's predictions show that: (1) At a low temperature of 0 ℃, the seepage amount reaches its maximum at 0.68 L/s, which decreases to 0.38 L/s at a high temperature of 20 ℃, and further reduces to 8.71×10?5L/s after repairing the seepage channel at 0 ℃. (2) The analytical and numerical simulation calculations of the U3 seepage amount are in good agreement, demonstrating the reliability of the seepage amount calculation. (3) After anti-seepage repairs, a simulated flood with a return period of one hundred years, i.e., a design flood level of 195.29 m and a check flood level of 195.5 m, results in a dam seepage amount of 0.67 L/s, with a slightly reduced dam foundation seepage amount of 2.16 L/s and 2.14 L/s, respectively.In conclusion: (1) Temperature and seepage have a clear negative correlation, with rising temperatures significantly decreasing dam seepage. The equivalent width of the dam seepage channel was calculated using the Cubic Law and the dam as a fracture, providing parameters for numerical simulations. (2) COMSOL software was used to calculate dam foundation seepage under different temperatures and water levels based on the geological conditions and dam structure at the dam site. The results show that seepage in the U3 section decreases with increasing temperature, with 0.68 L/s at 0 ℃ and 0.05 L/s at 40 °C, a difference of 12.6 times, indicating that low-temperature and high-water-level environments have a significant influence on seepage. (3) Seepage significantly decreases after anti-seepage reinforcement, therefore, it is necessary to promptly grout and seal the seepage channels to reduce the reservoir's seepage and ensure its normal and safe operation.