Eustatic sea-level changes strongly control the Earth evolution on paleogeography, paleontology and paleoclimate, as well as the distribution of petroleum and coal deposits. The controlling factors of eustatic sea-level changes are, however, still poorly understood partly due to lack of a high-resolution global sea-level curve. This paper reviewed the history of eustasy research, and summarized five types of approaches to reconstruct eustatic sea-level changes in deep-time, including stratigraphic, sedimentological, ocean basin dynamics, geochemical approaches and big data technique. We take the Cretaceous sea-level curve
as an example to describe the difficulties in reconstructing eustatic sea-level changes and the results displayed that promising prospects could be expected in this area.