Abstract: The southern coast of the Laizhou Bay represents a significant distribution area of subsurface brine resources in China, while also emerging as an area with the most representative and serious marine saltwater intrusion in China. In this study, 278 groundwater samples from the Tushan area along the southern coast of the Laizhou Bay were analyzed and tested. Based on the general standards for marine saltwater intrusion, combined with regional drilling data, this study summarized the spatial distribution characteristics of marine saltwater intrusion in the area. The results indicate that subsurface brine in the Tushan area exhibits a chemical type of Cl-Na, originating primarily from seawater. The brine concentration, ranging from 5.0 °Bé to 14.8 °Bé, exhibits a positive correlation with mineral content. The Cl⁻ concentration in subsurface brine ranges from 117.57 mg/L to 83 092.53 mg/L, with the saltwater distribution area reaching up to 137 km². Three confined brine layers are identified vertically, demonstrating a binary water quality pattern characterized by high and low salinity in the upper and lower parts, respectively. The results indicate that under the influence of continuous brine exploitation, the saltwater intrusion front shows a retreat trend in the Tushan area, with the saltwater distribution area thinking significantly.