Stable oxygen isotope ratio (δ18O) in ocean surface seawater is an accurate indicator of oceanic circulations. It can also be used to reconstruct paleoclimates. With the recent expansion of the sampling range and improvement in analytical techniques, research on δ18O in surface seawater has progressed markedly, yielding mainly improved knowledge of the δ18O distribution and source attribution. However, because of constraints on the range of oceanographic surveys, the spatio-temporal variations of oceanic δ18O remain incompletely characterized. In this study, the current research methods and recent progress pertaining to δ18O in ocean surface seawater were summarized, providing a reference for further research on oxygen stable isotope ratios in ocean surface seawater.