Abstract: Results of diatom analyzing and dominance calculating on 8 sediment samples of different depths indicates that dominant species are Paralia sulcate， Coscinodiscus radiates， C. excentrcus， Rhaphoneis surirella and 6 other species. P. sulcata， C. radiates and C. excentrcus are the highest dominant species as inner bay indicators fitting well to the environment of sampling sites. The relations of diatom assemblages and its locational landform to the sediment particle sizes were analyzed with clustering according to the species composition of marine， brackish water and freshwater distributed horizontally. Preliminary findings show that the diatom assemblages are affected by currents of Fuzhou River and Hongyan River and the alongshore SE current in Liaodong Bay in addition to the locational landform and distance from the estuarine．