Abstract: The gulf region is significantly impacted by human activities, with the problem of microplastic pollution becoming increasingly critical. This study investigates microplastic pollution in 13 surface seawater samples and 19 surface sediment samples from Laizhou Bay. The results show that the microplastic abundance in the surface seawater samples from Laizhou Bay ranges from 40.00 to 1480.00 items/m³, while the abundance in the surface sediments varies from 86.60 to 425.80 items/kg. In both the surface seawater and sediments, rayon is the most prevalent type of microplastic, followed by polyethylene terephthalate (PET). The microplastics are predominantly fibrous in shape, with transparency, black, and blue being the most frequently observed colors. Microplastics with a particle size of 500-1 000 μm account for the highest proportion. The distribution of microplastics may be influenced by factors such as river runoff, human activities, and ocean currents, revealing significant differences in microplastic distribution between seawater and sediments, as well as between the spring and summer seasons. Further analysis indicates that the similarity in microplastic characteristics among sediment sampling sites is greater than that among seawater sampling sites. Additionally, the potential sources of microplastic pollution in Laizhou Bay are varied, and these pollutants may continue to enter the bay through various pathways, thereby exacerbating the pollution issue. This study aims to identify the sources of microplastic pollution and their input mechanisms, which is of significant scientific importance for the protection of the bay’s ecological environment.