Much preliminary research has shown that the main destructive modes of rainfall on a single building of the Ming Great Wall in the Yuyang district include water erosion and gravitational erosion. The main factors affecting the single building include the characteristics of rainfall, the shape of site and the properties of the site soil. To further study the destructive modes and the function of the main factors at this kind of sites, experiments were conducted by using a scale model of single building of Ming Great Wall and interior simulated rainfall conditions based. These experiments show that the destructive rainfall modes on site models are consistent with the results of preliminary investigations. The main modes of water erosion include gully erosion, sheet erosion; the fluvial process, impact erosion and gravitational erosion included collapse and landslide. Commonly, in an A style rainstorm, all of these water erosion modes could occur, though gravitational erosion occur relatively less. In a B style rainstorm, both sheet erosion and gravitational erosion occurred primarily.