Abstract: The main external causes of ancient trees breaking and falling in nature are disastrous weather conditions. The ones that can directly damage ancient trees are wind, snow and freezing rain, which are briefly referred to as wind and snow load. At present, the damage methods of ancient trees are only divided into two types: fracture and loading, without further detailed research on the complex fracture behavior. However, as a multi-cellular layered biological composite material, tree wood has strong anisotropic properties in terms of mechanics. Ancient trees will undergo different fracture adamage modes under different force conditions. This is not only related to the anisotropic nature of the tree material, but also to the different internal forces caused by the morphological structure, as well as the size and location of the decayed cavities in the trunk. The hollow tree walls vary from thick to thin, and the ancient trees exhibit various fracture behaviors, such as bending fractures, torsional cracking, along the grain cracking, and crushing bending, etc. Understanding the mechanical mechanism of ancient tree destruction can guide the development of grading protection measures: when the ratio of the inner and outer diameters of tree trunk cavities is less than 0.7, priority should be given to conducting root and foundation stability tests. When it is within the range of 0.7 to 0.8, it is necessary to focus on investigating the potential high torque risk of the tree. If it is greater than 0.8, steel hoops should be added for reinforcement while suppressing the bending and torsional deformation. This research provides a solid scientific basis and operational guidance for precisely formulating extreme weather defense measures for ancient trees.