Abstract: The Xiaowan hydropower project double-curvature arch dam under construction is becoming the highest arch dam in the world. A lot of technical problems solved during construction must be world problems, and the project construction is a real challenge. According to research practice and understanding of key technology of hydropower engineering, main technical problems, such as construction treatment of high steep slopes of 700 meters, unload relaxation caused by rock excavation in the dam foundations, temperature control against cracks in the concrete arch dam, researches on flood discharge and energy dissipation as well as automization, and arch dam safety against earthquake, are tackled by the author in the study.