Abstract:The northwestern shore of the Bohai Bay is part of the sand bar- lagoon sedimentary system along the Bohai Bay. Its sediments contain rich information on the evolution of the geological environment, which is the key to understanding climate change and tectonism in this area. Based on the shallow stratigraphic sedimentary environment, sporopollen analysis and micropaleontological studies on the 80 m thick sequence above the QEJ01 hole in the northwestern coast of the Bohai Bay, combined with chronological data and quantitative paleoclimate reconstruction data, the vegetation evolution in the characteristic period since the middle Pleistocene in this area is discussed. To reconstruct the environmental evolution, the regional comparisons of the climate and environmental changes in the northwestern coast of the Bohai Bay at each stage of MIS6~MIS1 is carried out. In the QEJ01 hole sequence, between 450. 4~377. 14 ka, the vegetation type was mainly coniferous and broad- leaved mixed forest, the climate was warm and dry, and the sedimentary environment gradually evolved from a river bed to a coastal lake. From 377. 14~113. 96 ka, the climate was relatively cold and humid, and the vegetation type was mainly coniferous and broad- leaved mixed forest- steppe. The sedimentary environment was dominated by lacustrine and the later period is flood plain. Between 113. 96~98. 84 ka, the climate fluctuated frequently. It was mainly sparse tree desert grassland, the climate was cool and humid, the river bed was developed. From 98. 84~74. 33 ka, the climate was warm and humid, the vegetation landscape was coniferous and broad- leaved mixed forest- grassland. Precipitation increased, the sedimentary environment was mainly floodplain lake and riverbed facies. Between 74. 33~48. 09 ka, the climate was unusually cold and dry, and the sparse- desert forest was mainly coniferous forest. Grasslands were more developed. From 48. 09~25. 72 ka, the vegetation type was coniferous and broad- leaved mixed forest- grassland, the climate was warm and humid. Between 25. 72~22. 52 ka, the climate was cold and dry, the vegetation was sparse tree- desert grassland. 22. 52~3. 87 ka, the vegetation type was evergreen deciduous broad- leaved forest that evolved into coniferous- broad mixed forest- grassland, with a warm and humid climate, and the sedimentary environment was mainly delta plain. Between 3. 87~0. 0 ka, the climate was cool and dry, the vegetation type was mainly coniferous- broad mixed forest. The plain on the northwestern coast of the Bohai Bay is an active zone of tectonic activity. Since the MIS5 stage, the subsidence center has migrated from northwest to southeast, and the degree of development of the transgressive layer is controlled by regional tectonic movements and changes in climate and environment.