Abstract: Diatomite undergoes significant cumulative deformation under traffic loading, leading to engineering issues such as subgrade settlement, while research on its deformation characteristics under such loading remains limited. To explore the cumulative deformation rules of diatomite under traffic louds, a series of tests are carried out with different cyclic stress ratios, diatom contents, effective confining pressures, vibration frequencies and torsional shear stress ratios. The results show that the deformation resistance of diatomite is enhanced with the increase of diatom content; the rise in initial effective confining pressure and loading frequency aggravates strain accumulation, and the rotation of principal stress axes has a deformation-promoting effect. A deformation prediction model for diatomite is proposed, which embeds correction functions of diatom content and torsional shear stress ratio into the HCA model and optimizes the model parameters via the improved cuckoo search algorithm (ICS). The predicted values of the model are in good agreement with the overall trend of test results, which can effectively capture the cumulative deformation behaviors of diatomite. This research provides a scientific basis for the design and settlement prediction of transportation infrastructure in diatomite areas.