Abstract: In the field of roadbed engineering, the reinforced gravelly soil filling materials subjected to long-term upper loads are prone to phenomena such as intrusion of fine particles, leading to the deterioration of the mechanical properties at the reinforcement-soil interface. The pullout tests on the geogrid and gravelly soil with different contents of high plastic fine particles are conducted based on the factors such as pull-out rate relative compactness and normal stress. The influence rules of multi-factor coupling on the strength characteristics and volume change characteristics of the reinforced soil interface are discussed. The research findings indicate that under different pulling rates, the increase in fine particle content causes the pullout resistance curve to transition from hardening to softening, with the interfacial shear shrinkage gradually increasing. The particle contact state within the specimen at medium compaction is uneven, and the pull-out resistance curve shows a stepwise decline at content of fine particles the of 0%. The shear shrinkage is significant at low compaction density and high content of fines particles. When the normal stress is the same, an increase in the content of fine particles leads to a reduction in the peak pull-out resistance and displacement, constraining dilatancy. The comprehensive friction factor ratio is in a power function relationship with the normal stress and content of fine particles. The content of fine particles of 10% is the limit one of gravelly soil, and the pullout interface strength and deformation characteristics between geogrid and gravel soil change from dilatancy to shear shrinkage, and the interface strength decreases gradually.