Abstract: The gravity-arch dam of Dashankou Hydropower Station and its geologic and climate conditions are introduced. The design and construction demands of the dam's monitoring system are put forward. According to the monitored data, the temperature variation and cracks during construction periods, the displacements of the dam crest and abutment, the dam's seepage and stress during operating periods are analyzed. Results show that every monitoring value is within the limits, and the dam runs well.