The excavation and support construction of giant underground caverns in large-scale hydropower projects is a key route and a concentrated area of technical difficulties in engineering construction. Improving the excavation and support methods and construction machinery of underground power plants based on the actual geological conditions and working environment on site is an important guarantee for ensuring the safety, quality, efficiency, and green construction of underground caverns. This paper carried out innovative research, development and tackling of key construction methods and technical problems in the construction process of large underground caverns of Wudongde Hydropower Station, which included the excavation and construction of large-span high sidewall, excavation and construction of super large section surge chamber, excavation of small diameter slag chute shaft, support of super large section caverns in unfavorable geological sections, pipe pulling contact grouting construction, penstock assembly in the tunnel, concrete slip form construction of porous deep shaft and large outlet shaft construction, etc. Common key innovative construction methods and technologies from aspects such as process type, fine excavation, support, and equipment innovation technology were summarized. The research results could provide the reference for similar engineering construction.