Abstract: The design of supports for a deep foundation pit with an excavation depth of 15 m under an existing high-steep retaining wall 62 m in height is taken as an example. The specificity of ultra-high slopes and the existing problems in their design of supports are analyzed. Technical code for building slope engineering (GB50330), numerical simulation and engineering analogy method are combined for the design and effect evaluation of the supports. The monitoring results show that the design is effective to protect the high-steep retaining wall and large-scale public buildings. It may be a reference for other similar projects.