Abstract: This paper reported the distribution of phytoplankton biomarkers in surface sediments of Liaodong Bay, Bohai Sea. The distribution of biomarkers of three phytoplankton species, diatoms, dinoflagellates and haptophytes was not obvious in 51 surface sediments from Liaodong Bay. Biomarker contents were normalized to the total organic carbon (TOC) to eliminate the influence of grain size and sedimentation rate, it was found that the relative content increased from the bay to the estuary in Liaodong Bay. The primary productivity indicated by biomarkers is consistent with the results from modern water column phytoplankton surveys, indicating that the biomarkers can be used to reconstruct the primary productivity. The primary productivity in the Liaodong Bay is higher than that in the Bay mouth, which indicates that the main controlling factor is the turbidity of the water column rather than the input of terrestrial nutrients. The high primary productivity near Juhua Island on the west side of Liaodong Bay is mainly related to eutrophication caused by human culture and land-based sewage discharge. The relative proportion of biomarkers showed that diatom and dinoflagellate contributed more to the coastal area of Liaodong Bay, especially diatom occupied an absolute advantage, which was mainly related to the competitive advantage of diatom under the condition of high nutrient salts, while high haptophytes was found in the middle of Liaodong Bay, which corresponded to the invasion path of the Yellow Sea Warm Current (YSWC).