Abstract: Although loess typically exhibits low permeability,heavy rainfall events occurring once every few decades can trigger numerous shallow loess landslides on the Loess Plateau of northwestern China,leading to casualties,cave dwelling damage,and road destruction. To explore the mechanism of shallow loess landslides,this study proposes a modified method based on unsaturated soil theory. By incorporating the suction stress concept,a safety factor equation for hillslopes under unsaturated conditions is derived. Key parameters,including shear strength indices and suction stress under varying moisture contents,were obtained through consolidated undrained triaxial tests and TRIM tests. The method was validated using a typical loess landslide in the Yan'an loess area of northern Shaanxi Province. The results show that the safety factor decreases with depth in the saturated zone. When the potential sliding surface extends into the unsaturated zone,the safety factor continues to decrease with depth,reaching a minimum value of 0.99 at a depth of 2.4 m. The depth of the sliding surface in the unsaturated zone aligns with field investigation measurements.