Bohai Strait settled cross-sea project is an important part of the national railway network and the highway. Settled cross-sea channel will be built to replace the existing ferry transport, to meet the growing transportation needs. Based on the study of meteorology,hydrology, geology of Bohai Strait,the preliminary comparison of bridge or tunnel scheme and tunnel line position are analyzed. According to the analysis, Bohai Strait cross- sea project should adopt the whole scheme, and Lvshun—Penglai tunnel line bit program is excellent, the line position in deep tunnels is optimum. Because there are many technical difficulties of highway tunnel, as well as construction costs and operating costs are high, therefore, the railway tunnel scheme is the preferred one,and cars are carried by trains to cross the Bohai Strait tunnel.