Abstract: The paper reviews the concept origin of loess collapsibility and the research status of collapsibility mechanism based on its microstructure,and discusses on the collapsibility mechanism from the perspective of unsaturated soil mechanics,then puts forward the concept of generalized collapsibility.It is suggested that research of loess collapsibility includes the laboratory investigations based on field collapsibility stress-path and then building of constitutive model,as a base for engineering quantitative analysis and numerical simulation.One series(3 samples) loess moistening test under dead load shows that collapse occurs so suddenly at less than 1% of axial strain that deviatoric stress can not retain.Meanwhile,about 1～2kPa pore pressure raise is observed,indicating incompletion drained shear failure occurring in the collapse process.