The Jinping Ⅰ hydropower station is a huge water conservancy project consisting of the highest concrete arch dam to date in the world and a highly complex and large underground powerhouse cavern.It is located on the right bank with extremely high in-situ stress and a few discontinuities observed in surrounding rock masses.The problems of rock mass deformation and failure result in considerable challenges related to project design and construction and have raised a wide range of concerns in the fields of rock mechanics and engineering.During the excavation of underground caverns,high in-situ stress and relatively low rock mass strength in combination with large excavation dimensions lead to large deformation of the surrounding rock mass and support.Existing experiences in excavation and support cannot deal with the large deformation of rock mass effectively,and further studies are needed.In this paper,the geological conditions,layout of caverns,and design of excavation and support are first introduced,and then detailed analyses of deformation and failure characteristics of rocks are presented.Based on this,the mechanisms of deformation and failure are discussed,and the support adjustments for controlling rock large deformation and subsequent excavation procedures are proposed.Finally,the effectiveness of support and excavation adjustments to maintain the stability of the rock mass is verified.The measures for controlling the large deformation of surrounding rocks enrich the practical experiences related to the design and construction of large underground openings,and the construction of caverns in the Jinping Ⅰ hydropower station provides a good case study of large-scale excavation in highly stressed ground with complex geological structures,as well as a reference case for research on rock mechanics. The Jinping I hydropower station is a huge water conservancy project consisting of the highest concrete arch dam to date in the world and a highly complex and large underground powerhouse cavern. It is located on the right bank with extremely high in-situ stress and a few discontinuities observed in surrounding rock masses. Problems in may challenges related to project design and construction and have raised wide range of concerns in the fields of rock mechanics and engineering. Driving the excavation of underground caverns, high in-situ stress and relatively low rock mass strength in combination with large excavation dimensions lead to large deformation of the surrounding rock mass and support. Existing experiences in excavation and support can not deal with the large deformation of rock mass effectively, and further studies are needed .In this paper, the geological conditions, layout of caverns, and design of excavation and support are first introduced, and then detailed analyzes of deformation and failure characteristics of rocks are presented. Based on this, the mechanisms of deformation and failure are discussed, and the support adjustments for controlling the rock deformation and subsequent excavation procedures are proposed. of support and excavation adjustments to maintain the stability of the rock mass is verified. The measures for controlling the large deformation of surrounding rocks enrich the practical experiences related to the design and construction of large underground openings, and the construction of caverns in the Jinping I hydropower station provides a good case study of large-scale excavation in highly stressed ground with complex geological structures, as well as a reference case for research on rock mechanics.