Periodic water-level fluctuations in the Three Gorges Reservoir have resulted in differential distribution patterns of polycyclic aromatic hydrocarbons (PAHs) in soils across different elevations of the drawdown area. From the perspective of soil colloid–water level coupling, this study compared the colloidal characteristics and PAHs distribution in soils at multiple elevations (155–185 m) in the Xiangxi River bay before and after a complete water-level fluctuation cycle (from June 2022 to June 2023), aiming to reveal the redistribution mechanism of PAHs driven by artificial regulation of water levels. Results indicated that the total PAHs content in soils of the drawdown area decreased by 10.8–59.6% after water-level fluctuation. Soil colloids from different elevations exhibited high stability, which enhanced the transport of the PAH monomer phenanthrene (Phe) in porous media. Among all elevations, soil colloid properties and PAHs distribution at 165 m were the most sensitive to water-level variations. Fluctuations significantly altered soil colloid characteristics at this elevation: after water-level variation, the specific surface area of soil colloids increased by 70.7%, colloid particle size decreased by 13.3%, the absolute value of the Zeta potential increased by 18.8%, and the critical flocculation concentration (CFC) increased fourfold compared to pre-fluctuation values, indicating enhanced colloidal stability and transport capacity. Pearson correlation analysis confirmed that colloid stability and Zeta potential (p < 0.01) were the principal factors controlling PAHs distribution in the drawdown area soils during water-level fluctuations. This suggests that artificial water-level regulation drives the “sink–source” transformation of PAHs in soil by modulating colloid stability and physicochemical properties. These findings provide guidance for understanding the effects of water-level fluctuations on exposed-zone ecosystems and for managing PAH pollution in reservoir waters.