Abstract: With the intention of exploring the occurrence characteristics and sources of microplastics in the surface seawater of estuaries, mastering the distribution baseline of microplastics, and serving the protection and early warning monitoring of marine ecological environment, this study selected three typical estuaries in Hebei province, including Dapu estuary, Daqing estuary, and Nanpai estuary, to investigate the microplastic contamination. Through sampling, pretreatment, and identification, it was found that the abundance of microplastics in surface seawater in the coastal waters of Hebei Province is 0.14±0.11 n/m³, with particle sizes mainly concentrated in the range of 0.5-2.0 mm, and the predominant polymer type is Rayon, followed by polyethylene terephthalate (PET). Diversity index analysis indicates that the factors affecting the concentration of microplastics in estuaries are economic structure, human activities and catchment area of the river course. The extent and sources of microplastic contamination in different estuaries vary. The abundance of microplastics in the surface seawater of research area is generally at a relatively low level.