Abstract: Riverbank slopes often experience fine particle loss due to internal erosion under water flow scour, leading to the weakening of soil structure and subsequently triggering geological disasters such as bank collapse. To investigate the influence of fine particle loss on the mechanical properties of sandy soil, this study conducted a series of triaxial consolidated-drained (CD) shear tests to compare the mechanical behaviors of salt-bearing sands (with salt contents of 15% and 30%) and pure sand. The dissolution of soluble salt is employed to simulate the process of fine particle loss. The shear strength, stress-strain relationship, volumetric change characteristics, and critical state of sandy samples with different salt contents are systematically analyzed. The results indicate that under the same confining pressure, the peak deviatoric stress of the samples gradually decreases with increasing salt content, and the internal friction angle is significantly reduced. The salt-bearing sand exhibited continuous contraction throughout the shearing process, while the pure sand initially contracted and then dilated. However, the critical state lines of sandy samples with different salt contents in the deviatoric stress-mean principal stress plane essentially coincided, with no significant change observed in the critical stress ratio. The tests reveal the significant influence of fine particle loss on the peak strength and deformation behavior of sandy soil, as well as its limited impact on the final critical stress ratio. These findings provide important experimental evidence and a theoretical reference for riverbank erosion protection and slope stability assessment.