[Purposes] The paper aims to investigate the migration pathways and transport processes of microplastic after entering Dongting Lake. [Methods] Based on the field sampling data, the hydrodynamic model and the Lagrangian particle model were used to establish a numerical model of microplastic migration path and transportation in Dongting Lake. The differences in the migration pattern and distribution of microplastics in the lake between the water-stable period and the high water period are studied, and the reasons for the distribution of microplastic aggregation areas are explored and the sources of microplastics in the aggregation areas are analyzed.[Findings] The distribution of microplastics during the water-stable period showed significant non-uniform distribution, and there were four typical aggregation zones. Among them, the aggregation area at the East Dongting perennial water body is the largest, about 133 km2, and the proportion of microplastics discharged from Xiangjiang River in this aggregation area is 97.96%; the distribution of microplastics does not show significant aggregation during the high water period, but the overall diffusion area increases by 33% compared with that during the level water period. Comparative analysis of microplastics entering the lake with the four waters showed that the diffusion area of microplastics entering the lake from the Zijiang River was the largest during the water-stable period, while the diffusion area of microplastics entering the lake from the Yuan River was the largest during the high water period. [Conclusions] During the high water period, the ecological risk on the migration path should be paid attention to, while during the water-stable period, in addition to the migration path of microplastics, more attention should be paid to the ecological risk control at the aggregation area, and the focus should be on strengthening the control of microplastics entering the lake from Xiangjiang River and the management of microplastics in Xiangjiang River waterway, the perennial water body of Dongdongting, and the areas near the various sources of discharge. The results of this study can provide some reference for the management of microplastics in Dongting Lake.