Objective: There are rare cases that post in root canal dentin was debonded from root canal treated with sodium hypochlorite. The purpose of this study was to clarify the effect of ascorbic acid on the bond of resin abutment to root canal dentin on tooth. Materials and Methods: Post-cavities were formed in the bovine root canal and treated with sodium hypochlorite. Half of specimens were applied to sodium ascorbic acid, and a chemical and dual cured bonding system, and filled with composite resin for abutment. After storage in water at 37°C for 7 days, the root was cut from the coronal to the apical to a thickness of about 1 mm. Two-thirds of the samples obtained from one tooth were measured for bond strength by push out test, and the remaining one-third of the specimens were dye penetration for observing the bond interface and fracture region. Results: No significant difference in bond strength between with and without ascorbic acid treatment was observed regardless of bonding systems. However, some specimens without ascorbic acid treatment in the chemical and dual cured-bonding agents had observed gaps at the bonding interface and adhesive fractures comparison for those with ascorbic acid treatment. Conclusion: In the limitation of this study, there was no difference in bond strength of endodontically treated roots with or without ascorbic acid treatment, but the ascorbic treatment resulted in a decrease in the gap at the adhesive interface and an increase in the rate of mixed fracture or cohesive fracture.