Based on the demonstration application project of trapezoidal hollow spur dike in a 12.5m deep water channel below Nanjing on the Yangtze River, a numerical model of sediment movement was established. Combined with on-site monitoring data, the composition and habitat density of benthic animal communities around the trapezoidal hollow spur dike was analyzed. The Shannon-Wiener index, Simpson index, and Pielou evenness index were used to analyze the diversity of benthic animal species, and reveal the impact mechanism of local erosion and sedimentation evolution of the trapezoidal hollow spur dike on benthic animal communities. The results show that sediment on the bed surface accumulates in front of the trapezoidal hollow spur dike, with a median particle size of 0～0.25mm, which is beneficial to burrowing of benthic animals such as bivalves and oligotriches; the cavity inside the dam and the bed surface behind the dam are relatively stable, mainly composed of floating mud with a median particle size of 0～0.1mm, creating suitable feeding grounds and slow flow habitats for benthic animals such as chironomids and oligochaetas. According to the analysis of biodiversity index, the composition of local benthic animal communities around the trapezoidal hollow spur dike is relatively stable and diverse, and the trapezoidal hollow spur dike can provide habitats for different benthic animals and also provide rich bait and suitable habitats for aquatic organisms such as fish.