Reinforcement quality evaluation at the abutment is an important research direction.Prototype monitoring and theoretical derivation were integrated to study the replacement reinforcement quality in abutment contact zones of the Xiaowan ultra-high arch dam.The principles of monitoring layout and design are introduced in detail.Prototype monitoring shows that the increment of the interracial compressive stress is much larger in the impoundment stage than in the regulating stage.The water pressure and time-effect are two main factors affecting the interfacial stress.The time-effect is the key factor in the initial impoundment stage,and the water pressure is the key factor after impoundment.The contact properties are significantly improved by grouting.This study shows that there are three typical stages in the joint opening hydrographs,namely the compression stage,opening stage,and stable stage.There is a nonlinear relationship between the joint opening and temperature,which can be well described by the S-function.In conclusion,the reinforcement effect is satisfying,and the abutment is safe.