Abstract: Coastal intertidal wetlands are ecologically sensitive areas. Relying on the interaction of different landscape morphology and tidal hydrodynamics along the coast, the natural processes and ecological balance in the coastal waters are maintained. This paper studies the correlation between the landscape complexity and ecological environment (such as red tide and benthic biodiversity) in the offshore waters of the bay, and established a model of the correlation between benthic biodiversity and the complexity of coastal landform based on the water quality data of typical bays in China. And the fractal dimension model of fractal geometry such as fractal dimension and shape index were referenced in the modeling. Besides, with the help of SPSS statistical software, the modeling was implemented by least squares method. The results show that the complexity of coastline and spatial pattern play an important role in the coastal biodiversity and water purification function. Among them, the fractal dimension of the coastline is an important indicator. The research results can provide a stronger theoretical basis and reference for future quantitative control and management of coastal design, reclamation development and construction.