Abstract: Seawater intrusion is a global issue, exacerbated by increasing demands for freshwater in coastal zones. The development of
seawater intrusion has caused a series of ecological issues such as deteriorating groundwater quality and soil salinization. The research
on seawater intrusion not only has important theoretical significance, but also has important practical value for the sustainable
development of the coastal zones. Therefore, it is becoming more and more prominent in international research. With the development
of numerical methods and computational platforms, numerical simulation has become one of the most effective tools for studying
seawater intrusion problems. This paper summarizes the classification methods and standards of coastal zone types. From the
perspective of coastal hydrogeology, the coastal zones are divided into loose rocks and bedrock, which are generalized as equivalent
porous media and fracture-karst media. On this basis, the numerical simulation methods and their applicability of seawater intrusion on
the two kinds of media are analyzed. The current numerical simulation methods of seawater intrusion are comprehensively summarized.
In addition, the development direction of the numerical simulation methods of seawater intrusion are discussed. Besides, it is pointed
out that the transition band model with variable density and the discrete-continuum model will be the direction in further research.

Key words: seawater intrusion, numerical simulation, equivalent porous media, fracture-karst media