The construction conditions of Bohai Strait sea-crossing project are comprehensively analyzed on the basis of investigating existing various theoretical studies and collecting the data of meteorology and hydrology, topography and geomorphology, geology and rock activity characteristics and seismicity characteristics of Bohai Strait. The construction scheme of underwater bridge (immersed tube with small cross-section + pier) and shield is creatively put forward according to the existing engineering technology and the natural characteristics of the seabed in Bohai Strait. Benefits from vacuum technology, the train running resistance can be reduced to the minimum, and the train speed can be increased to over 1 000 km/h. Meanwhile, the passenger flow of similar sea-crossing projects in the world is analyzed, and the analytical results indicate the major cities around the Bohai Sea will become a one-hour metropolitan area and even an international megalopolis. Moreover, the new technical scheme adopted in this project can provide reference for the major sea-crossing projects in the future.