Abstract: In order to solve the pollution accumulating problem of high-speed train roof insulators in rainy and foggy winter environment, a hydrodynamic simulation model was built to study the pollution distribution characteristics of the roof insulators. The movement and forces of pollution particles in high-speed gas flow were analyzed by theory of fluid mechanics, and the particles' adhesion and separation behaviors after colliding to insulator surface were discussed by theory of agglomerating fluidization. On this basis, the optimization strategy to reduce the surface contamination was proposed. Analysis results show that the pollution at windward and lee sides of a roof insulator is more serious than that at lateral side in high speed air flow at low temperature. The pollutant mainly accumulates at the root of insulator shed at windward and lee sides, and only a little is adhered evenly on the insulator shed surface at lateral side. When the shed has no ribs, pollution is less and more uniform. In addition, the pollution density increases with an increase in the shed lower inclination angle, but decreases with an increase in the shed spacing. To achieve the minimum pollution density, the roof insulator shed should has no ribs on its lower surface, the shed upper inclination angle should be 8, and the shed lower inclination angle 0.