Abstract: The engineering geological conditions of Dalian subsea tunnel are complex. It is close to gas station, large ship manufacturing base and other buildings. Meanwhile, it is difficult and risky to pass through the existing subway, freight railway, military port and a large number of buildings. According to the characteristics and difficulties of subsea tunnel, the route scheme, construction method comparison, cross-section scheme, horizontal and vertical section scheme and shield segment design are studied. The main research conclusions are as follows: (1) Under the specific environmental conditions of the project, the construction method of cross sea tunnel adopts the scheme of single tunnel double track large shield with less environmental impact and low construction risk; (2) the deepest soil cover of the tunnel is the control condition of segment stress, and the maximum internal force is located at the vault; (3) considering the mechanical equipment and site conditions, 2 m segment ring width makes the number of circumferential joints in the tunnel the least, which is beneficial to improve the longitudinal stiffness of the tunnel, speed up the construction progress and reduce the cost; (4) the universal segment ring scheme with high assembly automation degree is adopted, which saves the number of steel formwork and is easy to rectify deviation; (5) the cross sea tunnel passes through the stratum with uneven hardness and soft, and the structural stress is relatively high. Considering the seismic requirements, the segment ring and longitudinal connection joints are all connected by inclined bolts.