Abstract: Landslides in the Badong Formation have long posed a significant threat to geological safety in northeastern Chongqing. To analyze the microscopic mechanisms underlying landslide evolution, field investigations, X-ray diffraction (XRD) tests, rock mass expansion tests, and disintegration tests were conducted to examine the distribution patterns, microscopic structures, and mechanical properties of Badong Formation landslides in Wushan County. The results reveal the following key findings: (1) Landslides in the study area are closely associated with the distribution of Badong Formation strata, with the second layer (T₂b²) and third layer (T₂b³) being the most prone to landsliding, accounting for approximately 71% of all landslides in the formation. (2) Landslides in the Badong Formation typically exhibit a layered sliding pattern, where the second layer (T₂b²) slides along the first layer (T₂b¹), and the fourth layer (T₂b⁴) slides along the third layer (T₂b³). Sliding surfaces predominantly develop within weak rock layers near strata contact interfaces, with significant variations in clay mineral content between the upper and lower strata of the sliding surface. (3) The swelling force induced by water absorption in the Badong Formation rock mass has minimal influence on oblique (edge) failure. The typical soft rocks in the first and fourth layers exhibit greater resistance to disintegration compared to those in the second and third layers. (4) After rainfall, the overall stability of Badong Formation landslides is more closely related to changes in the internal friction angle of the sliding zone soil than to variations in relative cohesion. This study provides a theoretical foundation for the prevention and control of landslides in the Badong Formation.