Abstract: In September 2020 and September 2023, surface sediment samples fromsediments were sampled at 44 stations inside and outside the using a clam sampler in Swan Lake inand Rongcheng Bay, Shandong Peninsula, East China, and the sample particle size and major elements were tested. Based on the test results, the plane distribution characteristics and differences of grain size and major elements inside and outside the lagoon were analyzed. Combined with correlation analysis, hydrodynamic numerical simulation, cluster analysis, principal component analysis and other methods, the main control factors of the distribution of major elements were explored. Results show that the sediment components of Swan Lake are mainly sand, and the sediment components of Rongcheng Bay are mainly silt. The grain size of Swan Lake sediment is obviously coarser than that of Rongcheng Bay. The average contents of SiO₂ and P₂O₅ in the sediments of Swan Lake (75.74% and 0.055%) were higher than those in Rongcheng Bay (61.73% and 0.053%), and the contents of major elements such as Al₂O₃, TFe₂O₃ and MgO were lower than those in Rongcheng Bay.Overall, the distribution of SiO₂ is opposite to the distribution trend of average particle size, and the distribution of most other major elements was similar to the distribution of average particle size. The contents of most major elements in Rongcheng Bay increased gradually from the shore to the open sea, and those in Swan Lake increased gradually from the shore to the lake. Particle size was the main factor affecting the distribution of most major elements ( SiO₂, Al₂O₃, TFe₂O₃, MgO, and so on) in the two lakes, and its impact on Rongcheng Bay was significantly higher than that on Swan Lake. The distribution of K₂O in the sediments of Swan Lake was affected by the erosion materials and their grain size from Chengshantou coast, and that in Rongcheng Bay was mainly affected by erosion materials. The distribution of P₂O₅ in the sediments of Swan Lake was mainly affected by human activities and seagrass beds, while that in Rongcheng Bay was mainly affected by grain size.