Abstract: Based on the analysis of surface sediments and columnar sediments from both sides of Bachimen seawall, and the comparison of water depth data in different periods, this paper analyzes the sedimentary environment and the changes of seabed erosion as well as deposition on both sides of Bachimen seawall.The results showed that the surface sediment types in Bachimen sea area were mainly clayey silt, and the sediment type tends to be single.The ²¹⁰Pb of columnar sediments did not decrease exponentially, indicating that the sediments were disturbed.The deposition rate showed that the deposition rate in the sea areas on both sides of Bachimen seawall gradually increased with time.The sea area was generally in the state of deposition.The main reasons for the change of erosion and deposition were the barrier of Bachimen seawall to the exchange of sea water between Dongshan Bay and Zhao'an Bay, the barrier of aquaculture cage, hanging aquaculture facilities and aquaculture pond to the sea current, the loss and residual bait as well as metabolites of aquaculture organisms in aquaculture, etc.