Taking the event of low temperature faced by Xixi reservoir dam due to climate anomaly for example, the effect of climate anomaly on Xixi RCC gravity dam was systematically studied. Through analyzing observational data of uplift pressure of dam foundation, the conclusion that low temperature and increase of reservoir water level lead to the increase in uplift pressure was drawled qualitatively. To further analyze the relationship between uplift pressure coefficients and the changes of temperature or water level, the statistical regression model of uplift pressure coefficient was established. Then, the effect of low temperature and reservoir water level on the dam safety was analyzed qualitatively. The results show that in high water level conditions, extreme low temperatures resulting in a larger temperature difference will affect the safety operation of RCC gravity dam. By calculating the strength and stability of gravity dam under high uplift pressure, the approach of determining the critical temperature of dam damage is obtained and the critical temperature of Xixi reservoir dam due to climate anomaly is derived.