From May 22 to 25, 2024, an advection fog event occurred along the coast of Qingdao. This study analyzes the microphysical characteristics of the sea fog at two coastal observation sites, Baguan Hill and Xiaomai Island, using data from an FM-120 fog monitor, surface automatic station observations, and ERA5 (ECMWF Reanalysis v5) reanalysis data. The results indicated that the fog event was characterized by stable weather conditions, southeast warm moist airflow, and a strong inversion layer. During the event, the average number concentration at Baguan Hill is 277.02 cm^?3, with an average liquid water content of 0.051 g m?3^{, an average effective radius of 4.92} μm, and an average radius of 2.65 μm. At Xiaomai Island, the average number concentration is 77.58 cm^?3, with an average liquid water content of 0.027 g m?3^{, an average effective radius of 7.39} μm, and an average radius of 2.78 μm. The microphysical characteristics from both observation points exhibited synchronous temporal evolution, and the droplet size distribution displayed a distinct bimodal structure during the development and maturation of the fog, particularly evident in the large particle range above 15 μm. The visibility parameterization scheme established based on both number concentration and liquid water content shows optimal predictive performance during the fog event.