In this paper, pore water was extracted by mechanical squeeze in a bore of Caofeidian with a depth of 0~100 m. The analysis of porewater indicates that the pore water is alkaline, and the total dissolved solid is between 7.26 and 26.89 g/L, decreasing with depth; and Cl/Br in continental sediment tends to infinity, while that in marine sediment is 279~280. It can be concluded that the pore water is sedimentary water revealing the freshwater and seawater characteristics in continental and marine sediment respectively with no clear signs of modern seawater intrusion. The reconstruction of Late Pleistocene temperature is 5.21~5.81 ℃ using δ¹⁸O, with much higher temperatures calculated by shallow data within 40 m attributed to mixing and diffusion of modern pore water.