Abstract: Plaeotemperature variation of ocean surface water is critical for understanding global paleoenvironmental change and future climate trend. Previous researches on this topic were mainly devoted to the Quaternary period. Paleotemperature changes of oceanic surface water in the period of 30 and 45 Ma are little known. In this paper, using the sediment samples obtained from 17 sites of the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP) and foraminifera oxygen isotopic data, we calculated the average temperatures of the global ocean surface water at 30 and 45 Ma, respectively. Isothermal contour maps of these two periods are compiled together with the climate zones induced from continental climate markers. The temperature variation pattern is also summarized. Our results show that the temperatures of the global ocean surface water were gradually getting colder from Eocene to Oligocene, but the average temperatures of these two periods were significantly higher than that of the modern ocean surface water. It provides new evidence for the further study of the global paleoclimate changes.