The numerous check dams constructed on the Loess Plateau are facing significant risks of failure, with progressive hydraulic failure being one of the primary modes. This study establishes a theoretical model for progressive hydraulic failure of loess check dams (LCD), based on the Janbu method and upper bound limit analysis method. The model incorporates multiple factors, including pore water pressure, hydraulic gradient, height of the phreatic line, depth of rainfall infiltration, and crest crack, while also considering the geometric structural evolution during the progressive failure process (PFP). Additionally, the modified Morris screening method is employed to assess the influence of various factors on dam stability at different failure stages. The results indicate that hydraulic gradient and pore water pressure are the key factors affecting dam stability, with the optimal monitoring location being the middle-lower part of the dam slope. A simplified theoretical model for progressive hydraulic failure of LCD is established, with key factors (pore water pressure and hydraulic gradient) as monitoring indices, determining the evolution of the dam stability coefficient during progressive failure. Furthermore, considering the time-variability of the dam geometry and hydrological parameters during the PFP, a multi-stage safety factor reduction rate is introduced. Subsequently, a risk level classification method for the progressive hydraulic failure of LCD is proposed, enabling early warning of dam instability at different failure stages. The findings provide theoretical support for ensuring the safety of LCD and mitigating instability risks.