Shenzhen-Zhongshan Crossing-river Link ( Shen-Zhong Link) is the key project in G2518 of National Expressway Network, across the Pearl River Estuary. Shen-Zhong Link is a mega project integrating bridges, artificial islands, tunnel, and underwater interchanges, which is built according to the standard for bi-direction eight-lane expressways. The total length of the project is 24 km, of which the tunnel is 6 845 m long, constructed by immersed tube method. Through experimental researches, analysis and demonstration, the technological requirements and construction process for the steel-concrete-steel composite structure of the rectangular immersed tube, the pre-laid gravel cushion and the underwater deep cement mixing (DCM) pile foundation treatment. In addition, a series of special construction equipment, such as the self-propelled huge barge integrated with the floating, towing, immersion and installation functions is developed.