In order to solve the technical problems that Shantou Su′ai Tunnel encounters, i.e. seabed hard rock, boulder group, high seismic fortification intensity， etc.〖KG-*3〗, a deep study focusing on the crosssectional, plan and longitudinal profile design schemes is made. Some conclusions are drawn as follows: (1) Comparison is made between twintube and tripletube scheme, which shows no essential distinction in terms of seabed hard rock; while twintube scheme is superior to tripletube scheme in terms of firefighting, connection gallery and construction and seismic resistance risk. (2) The study of seismic resistance, cost, structural force and tunnel operation and maintenance shows that shield segment with singlelayered precast structure is superior to that with builtin secondary lining structure. (3) The seabed hard rock and boulder group conditions, dock, harbor, anchorage, etc. should be surveyed before tunnel plan design scheme determination. (4) The seabed hard rock and boulder group conditions, minimum cover soil, planed elevation of main channel, harbor, etc. should be surveyed before tunnel longitudinal profile design scheme determination to reduce construction difficulty and risk.