【Objective】Jiangnan garden rockeries are a critical aspect of garden heritage. The widespread issue of plant root splitting poses a serious threat to the longevity and preservation of these rockeries. Incorporating the study of plant root splitting into the preventive protection system for rockeries can strengthen the system’s foundation, leading to a more effective preservation of garden heritage.【Method】This study uses the Zhanyuan Garden in Nanjing as a case study to quantitatively analyze the mechanism of plant root splitting in rockeries. It identifies problematic tree species, proposes and verifies five plant variables significantly related to root splitting, and establishes a regression prediction model for the area of cracks caused by this phenomenon.【Result】The study found that tree species with straight and deep roots are more likely to cause cracks in artificial rockeries. In the Zhanyuan Garden, the most significant root splitting was observed in Puja and privet, followed by loquat, Longjaya sophora, Magnolia, and papaya. Five factors,namely root length, root diameter, canopy width, tree height, and base diameter,were identified as highly influential in root splitting, showing significant correlations with the area of the resulting cracks. A multiple regression analysis helped to construct a preliminary prediction model for rockery crack areas, setting a warning threshold for changes in rockery crack dimensions. It was suggested that inhibiting the growth of a single root system might be necessary if the root length changes by more than 11.25 cm while the diameter remains constant.【Conclusion】Plant root splitting accelerates the development and expansion of cracks on rockery surfaces, potentially leading to stone fractures and structural collapse, thus endangering the heritage’s long-term preservation. Based on the quantitative analysis, refining environmental variables, categorizing monitoring levels, and defining clear warning indicators can enhance the predictive capabilities and quantitative assessments for rockery protection. These measures aim to facilitate timely interventions to mitigate the impact of root splitting and improve the overall preventive protection system for rockery heritage.