Abstract: Loess, widely distributed across northwestern China, is a Quaternary aeolian deposit characterized by its pronounced collapsibility. Owing to its naturally metastable structure, loess presents high strength under low-moisture conditions but may experience significant deformation when subjected to loading/wetting, thereby triggering serious geohazards such as landslides and subsidence. This paper comprehensively reviewed the micro-macro mechanisms, theoretical models, and evaluation methods of loess collapsibility. By comparing the microstructures, water retention properties, and compression and shear behavior of intact, compacted, and reconstituted loess, the coupled effects of soil structure and suction on collapse properties were elucidated. Furthermore, an elastoplastic constitutive model incorporating coupled structure-suction effects, and a simplified method for evaluating loess collapsibility, were developed. Combining the proposed simplified method with machine learning techniques and time domain reflectometry (TDR), an approach for in-situ rapid evaluation of loess collapsibility was proposed. These studies provide both theoretical and technical support for the assessment and mitigation of loess-related geohazards and engineering issues.