The cranny of the stacking mud wall of Jiaohe Ruins is a typical damage found on earthen structures. Grouting is a valid method to repair the cranny of earthen structures. The research of grouting focused on two problems, the material and the construction craft. According to indoor and onsite experiments, PSC with a 3.7modulus, a 12% concentration and a 0.600.65water to cement ratio performed well in reinforcing structures with cranny. Through research on the construction craft, guidelines were provided for reinforcing earthen structures with crannies in terms of cranny occlusion, grouting pipe layout, grouting tools,penetration into cranny walls and the grouting process.