Abstract: This study mainly analyzes and summarizes the relationship between the apparent resistivity and chloride ion concentration in the process of determining the seawater intrusion boundaries of suspected seawater intrusion areas in Qinhuangdao coastal areas using results obtained by the high-density resistivity method. Firstly, this study conducted the statistical analysis of the corresponding relationship between apparent resistivity values obtained through resistivity logging in different geological zones and the chloride ion concentration obtained from water samples collected from corresponding wells. Based on this, the correlation between them was obtained through mathematical analysis, and then the corresponding linear relationship between them was determined. Finally, seawater intrusion areas in the study area were delineated using this relationship combined with the measurement results obtained by the high-density resistivity method. The research process and the final linear relationship will provide experience and methodological guidance for the follow-up work in similar regions.