Loess exhibits typical water sensitivity and dynamic vulnerability. The combination of rainfall and earthquakerelated issues presents a complex disaster process, posing a significant threat to the infrastructure in the loess region. A cyclic simple shear test was conducted on undisturbed loess under a constant vertical stress ranging from 50 to 300 kPa, comprising three stages(C-W-D): consolidation, pre -humidification, and cyclic loading. The deformation behavior under humidification and cyclic loading was analyzed. The microstructure evolution of loess during three stages was examined using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). Results indicated that: (1) Cyclic deformation increased with the rise in vertical stress sigma v , humidification parameters S w , and dynamic shear stress amplitude gamma d . The sensitivity of cyclic deformation to sigma v and gamma d gradually decreased as S w increases. (2) The total deformation in the three stages correlated positively with S w , sigma v , and gamma d . The proportion of humidification deformation and cyclic deformation in the total deformation was largely unaffected by sigma v , with cyclic deformation gradually dominating as gamma d increases. (3) The prehumidification stage promoted aggregates and the formation of numerous intergranular pores. Cyclic loading mainly leads to the change of pore structures, forming obvious seismic damage area. Based on the relationship between humidification deformation and cyclic deformation, a loess deformation prediction model was proposed, which can comprehensively consider S w , sigma v , and gamma d . This can provide a theoretical reference for earthquake disaster prediction in collapsible loess areas.

来源平台：ENGINEERING GEOLOGY