We studied the ultra-deep and ultra-hard underground diaphragm wall in conjunction with the foundation pit support project of Shenzhen Evergrande Center in this paper, and analyzed the key technologies in the process of slotting the ultra-deep and ultra-hard underground diaphragm wall. During the construction process, the construction technology of rotating-gripping-milling trenching suitable for super-deep and super-hard geology was adopted, and a special pilot hole method was developed to effectively control the perpendicularity of trenching, which overcame the key problems of low construction efficiency and poor verticality of trenching for super-deep and super-hard underground diaphragm walls. The relevant trenching technology can provide reference for the construction of underground diaphragm wall with ultra-deep and super-hard rock penetration.