Abstract: The present design specifications for the arch dam assume that the water level in the reservoir is normal at the normal water level for computing temperature loads, however, the water level varies continuously in fact. The research results show that there exists a large difference of the temperature loads between the normal water level and changing water level. This paper takes an arch dam located at the southeast of China as an example. According to the temperature changes at the same elevation, the annual temperature change is expanded by Fourier series, the temperature loads at different water levels are analyzed, and some comparisons are made for the stresses and deformations under temperature loads at the normal water level and the changing water level. The analysis results show when the depth of water increases, the difference values of the temperature loads at the normal water level and the changing water level increase first and then decrease. While other loads keep constant, the stresses and deformations under the temperature loads at the normal water level are greater than those at the changing water level.