Abstract: Ground fissure disasters are slow-occurring geological disasters, the most common of which is the buried ground fissure, characterized by abruptness. The large influence range and potential disaster effects of buried ground fissures are urgent problems that need to be solved. The buried ground fissures are mainly normal faults that are widely distributed in areas with loess formation. A large physical test model and a discrete element model of buried ground fissures in loess formation were established to study the fracture extending mode, the variation law of stress, and surface displacement in overlying soil caused by the activity of buried ground fissures with a dip angle of 60°. The characteristics of fracture extension were analyzed, and the whole process of fracture extension was summarized. The results show that the rupture zone of the hanging wall is obviously larger than that of the footwall. Under the activity of the buried ground fissure, tensile deformation is the main form of the overlying soil, and an inverted triangle fracture zone appears. The soil pressure variation in the soil is related to the soil arch at the top of the cracks and the toppling deformation toward the direction of the hanging wall. The fracture extension process of buried ground fissures can be divided into six stages: the initial activity stage of buried ground fissures, the generation stage of reverse dip cracks, the generation stage of near-vertical fractures and reverse dip cracks extending stage, the synchronous expansion stage of near-vertical cracks and reverse dip cracks, the connection stage of near-vertical cracks and buried ground fissures, and the stable deformation stage of ground fissures. The above simulation results can provide a basis and reference for engineering construction and disaster prevention in areas with ground fissures.