Abstract: FromJanuary to the beginning ofMarch 2007, the water level at Dongfeng hydropower station was above 960 m, and during this period, the temperature here was low. Under condition of lowtemperature and high water level, average horizontal displacement, especially the radial displacement of the damwas larger than the same periods in other years, and some of themwere the maximum in history. This paper, by introduction to this, with observation data, explained the influence of low temperature, high water level and time effect to damstructural safety. Hopefully, it would be useful in operation and deformation monitoring.