Abstract: Holocene transgression in the Gulf of Bohai Sea was an important event of global climate change in the Late Quaternary. Previous studies have shown that Holocene transgression on the west coast of the Bohai Bay has penetrated into Wen'an County. The authors discovered a new species of genus Sinonovacula in 8^th layer along the 15BZ02 profile in Xiongxian County of Hebei Province, 30 kilometers east of Wen'an County. These new species are perpendicular or oblique to the formation, and inhabited in the medial tide and low tide of the intertidal zone of the estuary. Besides, marine-ostracoda Tanella opima were discovered in this layer, which shows that sea water transgressed into Xiongxian areanearly 6970~6670cal a BP in Middle Holocene.