【Objective】Microplastics contamination is an aggravating environmental problem threatening the marine ecosystem, where it has spread globally even to the remotest habitats. Extremely small in particle size (<5 mm), microplastics have been found in high density in waters and sediments, and are interacting with organisms and the environment in a variety of ways. Microplastics in the environment have the characteristics of being extremely small in particle size, hydrophobic, and capable of carrying persistent organic pollutants (pops). A wide range of marine organisms have been found to have ingested microplastics by mistake as food, thus leading to loss of nutritional value of diet, physical damage and exposure to pathogens. In addition, microplastics are ready to adsorb toxic hydrophobic organic contaminants, which arouses the question of what risk of chemical exposure aquatic biota faces from microplastic-associated contaminants. Moreover, the presence of marine microplastics in seafood could pose a threat to food safety for mankind. 【Method】The Nanji National Nature Reserve, and the estuaries of the northern branch, the mid branch as well as the southern branch of the Ganjiang River were selected as objects of this study. Sediment samples were collected from 12 sampling sites for isolation of microplastics therein by flotation separation, and exploration of distribution and composition of the microplastics in the sediment. Data were analyzed with one-way ANOVA. 【Result】Results show that in terms of microplastics abundance in the sediment, the four regions appeared to follow an order of the mid branch > the southern branch > Nanji > the northern branch, varying in the range of 1 452±221 ind•kg^-1, 1 285±69 ind•kg^-1, 102±65 ind•kg^-1 and 11±6 ind•kg^-1, respectively. Microplastics abundance in the sediment varied with water regime of the regions, exhibiting an order of dry season > normal season > rainy season. The microplastics in the sediment were dominated with foam, and then fiber in of Naji, mainly with fibre in the northern branch, and mainly with fragments in the middle and southern branches, accounting for more than half of the total amount of microplastics. Microplastics in the sediment were mostly 2~3 mm in particle size, and some 3~4 mm in Nanji and mostly < 1 mm in the branches, which making up more than half of the total microplastics. The microplastics in the Ganjiang River varied in particle size and displayed an order of <1 mm > 1~2 mm > 2~3 mm > 3~4 mm > 4~5 mm in particle size composition. The larger in particle size, the smaller in proportion. The microplastics differed greatly with type in surface morphology and roughness. Fragment microplastics were various in color and shape, with rough surface and obvious signs of wear. Fiber microplastics were smooth, linear and mostly blue in surface. Foaming microplastics were mostly white, light in texture and various in shape. Film microplastics were smooth, soft and irregular. There was great variability in composition of microplastics with type. The microplastics in the Ganjiang River were composed mainly of polyethylene and polypropylene. 【Conclusion】 Microplastics abundance is closely related to human activities, and the microplastics in the Ganjiang come mainly from the decomposition of daily plastics supplies and packaging, such as fertilizer and cement bags. Overall, all the findings in tthis study provide strong evidence of the high levels of microplastics pollution in the Poyang Lake, and suggest that more attention should be paid to monitoring microplastics pollution of the Poyang Lake.