Abstract: To explore the occurrence characteristics of microplastics in reservoir water and organisms, Wudu Reservoir was selected as the research area, and microplastics in surface water of different areas and fish in the reservoir were sampled and analyzed in the wet period in 2022. The results showed that the average abundance of microplastics in the surface water of Wudu Reservoir in September 2022 was (63.61±16.26)n/L, and there was no significant difference in the abundance of microplastics at the head, middle and end of the reservoir. Moreover, the average abundance of microplastics in the gastrointestinal tract, gills and muscle was (13.61±8.43), (12.22±4.99), and (4.66±3.34)n/g, respectively. In addition, the abundance of microplastics in muscle was significantly lower than that in the gastrointestinal tract and gills (P<0.05). The results of microplastic composition and size analysis showed that polyvinyl chloride (PVC) and polyamide (PA) accounted for the largest proportion of microplastics in both water and fish, and microplastics with small particle size (20-50 μm) were mainly in both water and fish. The results of correlation analysis showed that the chemical composition and particle size composition of microplastics in surface water were significantly correlated with those in fish (P<0.05). The research results could provide data support for the microplastic pollution control scheme of lake and reservoir.