As an emerging marine environmental issue, marine plastic debris pollution has attracted worldwide attention. Studies have covered more and more areas of the world’s oceans. To further understand the sources and variation of marine plastic debris in the surface water of the Bohai Sea, in this study, plastic debris was collected during the four seasons of 2016-2017. The results showed the mean density of plastic debris over these seasons was 0.49 +/- 0.18 particles/m(3). Macro-, meso-, and micro- plastics accounted for 5%, 26%, and 69% of the total number of plastic debris, respectively. The density of the microplastics was 0.35 +/- 0.13 particles/m(3). The highest density was found in spring, followed by summer and winter, and the lowest in autumn. High distribution densities were observed in the Liaodong Bay and the Bohai Strait, which were attributed to the dynamics of the rim current, terrain, and fishery activities. Capsule abstract: Riverine input, dynamics of the rim current, terrain, and fishery activities contribute to the variations in marine plastic debris in the surface water of the Bohai Sea.