Abstract: The interface cracking between the rammed earth supplement and the original site body, after construction, is a common issue for the reinforcement of the erosion area at the base of rammed earth sites. The study conducted on-site reinforcement experiments with four crack prevention measures: no-crack measures (WZ), setting a cushion layer (DC), interface anchoring (MG), interface grooving (KC), and a combination of cushion layer + interface anchoring + interface grooving (DMK). It included continuous and synchronous monitoring of strain and moisture content. The study analyzed the development of macroscopic cracks at the interface, daily interface strain, and accumulated plastic strain under each measure, explaining the crack prevention performance and mechanisms. Results indicate that under the five operating conditions designed in this study, during rapid moisture loss, the development of macroscopic interface cracks, daily interface strain, and accumulated interface plastic strain consistently ranked from largest to smallest as follows: WZ > DC > MG > KC > DMK, with DMK showing the best crack prevention effect. Under this model, the interface bonding strength is mainly borne by the interfacial adhesion, the anchoring force of the anchor bolts, friction and shear pin force, and the interlocking and bonding force of the groove.