Spur dikes play an important role in improving river ecology, and in engineering practice, permeable spur dikes with both stability and permeability are widely adopted. Based on generalized flume-model experiments, this study examines the distribution characteristics and mechanisms of insoluble pollutants around permeable spur dikes under different porosity and pore size conditions. The results indicate that high porosity or large pore size enhances water infiltration and jet effects, allowing more pollutants to enter and remain in downstream areas and recirculation zones; porosity and pore size have relatively little influence on pollutant concentration at the upstream slope but exert a greater impact on the recirculation zone and downstream slope; variations in flow discharge primarily regulate pollutant distribution by altering flow velocity and residence time. These findings suggest that by optimizing porosity and pore size, downstream pollutant accumulation can be reduced while maintaining structural stability, thereby balancing hydrodynamic exchange and habitat quality and providing important guidance for the design of ecological spur dikes.