Abstract: Loess landslide hazards in Northwest China is gradually gaining attention, especially loess-mudstone landslides, their destabilization mechanism and mechanical model have become a hot spot for research in the direction of geotechnical engineering. Using sliding deformation as an indicator, we studied the progressive instability model of loess-mudstone landslides, which can better serve the monitoring and early warning of loess-mudstone landslides. Direct water infiltration at the sliding interface was used to simulate the characteristics of progressive sliding instability of loess-mudstone landslides under the action of rainfall infiltration. Miniature pore water pressure and soil pressure sensors were arranged at the sliding interface and macroscopic deformation observation points were arranged at the sides and surface of landslide, to reveal the progressive sliding instability characteristics of the loess-mudstone landslide. The results show that the loess-mudstone landslide forms tension cracks at the top or middle of the landslide, and then the cracks gradually expand and divide the landslide, forming a three-stage instability model of "sliding - pulling - pushing". The modelling for progressive sliding instability of loess-mudstone landslides provided important scientific value for its monitoring, early warning, and engineering defense.