The development of underground urban space in Shanghai requires that the depth of the retaining structure of the underground foundation pit exceed 100 meters. Based on the practice of 120m ultra-deep diaphragm wall test section, combined with relevant research, grooving technology, slurry system, reinforcement cage fabrication and hoisting, joint waterproof treatment, bottom cleaning treatment measures, concrete pouring, testing, molding quality, etc., this paper summarizes the quality control points of the construction of ultra-100m deep diaphragm wall in Shanghai soft soil foundation, with a view to providing reference for similar projects.