Abstract: Seawater intrusion has emerged as a significant coastal hazard in our country, profoundly impacting the ecological environment and sustainable development of coastal regions. The high-density resistivity method offers notable advantages, such as cost-effectiveness and efficiency, in delineating the extent of seawater intrusion and identifying its boundary. However, it also presents challenges, including the potential for multiple interpretations of results, which hinder the establishment of a standardized criterion. This study conducted a simulation experiment on seawater intrusion, considering the influence of tides. By analyzing the impact of various factors on formation resistivity, and examining the relationship between frequency, amplitude characteristics and simulated tide level data using the continuous formation resistivity observation method, the researchers successfully outlined the scope of seawater intrusion. Consequently, they overcame limitations associated with multiple solutions in single-section resistivity measurement and proposed a novel approach to determine the seawater intrusion interface based on the continuous high-density resistivity method.