Abstract: Marine geological big data is an important part of geological big data, and has significant value in supporting the exploration and development of marine mineral resources and major marine engineering construction. This article combines the construction practice of the National Marine Geological Database and provides the definition of marine geological big data. The characteristics of massive volume, multi-source heterogeneity, spatiotemporal coupling, and confidentiality sensitivity of marine geological big data were analyzed, and the key technologies in big data storage management platforms, multi-source data fusion, distributed computing, big data analytics, and security control around the five essential stages of the marine geological big data lifecycle—collection, storage, processing, analysis, and service, were explored, aiming to fill gaps in previous research and establish an interdisciplinary theoretical framework.