Abstract: Based on the surface sediment samples collected in 2022, the sedimentary dynamic environment and sediment source of Wuyuan Bay and Tong'an Bay mouth were studied by end-member analysis method. The results showed that three unimodal end-members were extracted using surface sediment grain size end-member analysis. The EM1 components represented the sedimentary environment with shallow water depth and weak hydrodynamic force, which could be used to indicate the sediments entering the sea form the rivers and the fine particulate matters in the Taiwan Strait with the rising tide. EM2 components represented the sedimentary environment with strong hydrodynamic effect and significant mechanical differentiation, and could represent the terrestrial clastic materials eroded by coastal weathering. The EM3 components represented the sedimentary dynamic environment under the disturbance of stronger human activities, and represented the bottom sand material before the large-scale deposition of Tong'an Bay affected by human activities such as Gaoji seawall and reclamation. Recently, human activities such as Gaoji sea dyke opening project, bridge construction, channel and harbor dredging and reclamation had disturbed the sedimentary environment of the study area, and the gravelly coarse sand substrate had been exposed.