The interface bonding quality is critical to the repair effect of repaired cementitious materials. In present, there is no proper method to accurately evaluate whether the interface can establish the effective mechanical connection. This work proposed a method to visualize the interface bonding effect of cementitious materials repaired zone. The volume images on three repaired mortars with different bonding areas during loading process were obtained via in-situ X-ray computed tomography. The digital volume correlation (DVC) was employed to analyze the volumetric strain distribution of samples based on the obtained images. As there is no constraining in de-bonding area, a greater deformation occurs in the loading process than in the bonded area. Therefore, the area without a mechanical bond in the repaired mortar can be visualized through the strain mutation in the DVC strain contour. The results show that the strain mutation area detected in the DVC results corresponds well with the artificial de-bonding area, indicating that this method can detect the de-bonding area in the repaired mortar.