Shiziyang Tunnel under construction on FoshanDongguan Intercity Railway, which has the significant characteristics of large diameter (13.1 m), high hydraulic pressure (0.78 MPa max.), complex geological conditions (full crosssection of composite strata, three fracture zones and two underwater faults), long distance of blind heading of shield (4.9 km) and high running speed of train (200 km/h), etc, is the 2nd shield tunnel crosses underneath Pearl River Estuary Shiziyang Sea. In this paper, the engineering comparison, data research and experience summary are carried out, and the overall design and key technologies for Sizhiyang Tunnel are introduced. And then, a series of problems, i.e. selection of depth of underwater shield tunnel in bedrock strata, segment circular dislocation control, segment joint waterproof under high hydraulic pressure, settlement control of weak base soil under cyclic load and synchronous construction of internal structure, are proposed and solved. Finally, the doubledoping steel fiber and polypropylene fiber which can improve fire resistance capacity of shield tunnel segment are proposed; and the shield type selection in composite strata (especially in fracture formation) and shied chamber opening technology under high hydraulic pressure are discussed.