The issues such as cutter spacing arrangement, cutterhead structure analysis and cutterhead function optimization in the design of superlarge diameter shield cutterhead boring in submarine complex strata are very important. Hence, the working conditions of a shield bay tunnel crossing fullface soft strata, soft strata intruded by boulders and bedrock protruding strata are analyzed in detail based on geological and hydrological conditions of the project. Firstly, the indoor rock breaking tests with different cutter spacings are carried out to determine the cutter spacing in the central area, and the general layout scheme of the cutterhead is proposed. And then the static and modal analysis of the cutterhead structure are carried out by numerical calculation, and the results show that the maximum structural stress reaches 190 MPa, the maximum deformation reaches 6.2 mm, the first six natural frequencies range from 26.6 Hz to 42.9 Hz, and the natural frequencies avoid the working frequencies. Finally, the cutterhead optimization methods, i.e. centralized control and distributed scouring system, cutter running condition monitoring and wearresistant protection measures are put forward. The application results show that the cutter spacing is rational, the cutterhead structure can meet the requirements of strength and stiffness, and the cutterhead optimization methods can improve the adaptability of shield in silt and hard and soft strata. The results can provide reference for shield design and selection in similar projects in the future.